Deleting a table from MySQL database in Django manually - mysql

During my experimentation with my blog app (blogapp) in Django, I created two models (Category and Language), connected them to another model (Post) using following connections:
category = models.ManyToManyField(Category)
language = models.ForeignKey(Language)
Then it gave an error like THIS due to the lack of default value. Tried to roll that back by using an amalgam of THIS and THIS. Then I tried to add a default value using THIS. I've got an error "django.db.utils.OperationalError 1050, Table XXX already exists", then I tried THIS. Tried to revert back migrations by deleting the created migrations from the migrations folder manually. At some point I got django (1054, "Unknown column in 'field list") error.
Finally I decided to revert back to my original starting place. When I connect to my MySQL database using python manage.py dbshell, I realized that my MySQL server still have two tables that should have been deleted, blogapp_category and blogapp_language. Server is working properly but I keep getting "Table XXX already exists" error when I try to add those models.
Dropping tables from MySQL seems to be the only option at the moment.
When I run
mysql> SHOW COLUMNS FROM blogapp_post;
I did not see any reference to language or category, i.e. no columns named language_id or category_id. I have two questions at the moment:
Is it safe to delete tables manually using:
DROP TABLE blogapp_language;
DROP TABLE blogapp_category;
Will there be any negative effects?
Is there a way to freeze database like git so that when I revert to the old database, such tables added to the database by django migrations automatically dropped??


Delete respective entry from table django_migrations.
Delete migration folder from your app.
Delete table created by the app.
Now do makemigrations and migrate.
You can revert back using git but there will be errors and data correction requirements.

Related

MySQL can't show table after altering auto_increment

I created two tables like this
and I want to change the added data's id so I use
alter table member auto_increment=5;
after this, it couldn't show my member table. It shows
error 2013: lost connection to MySQL server during query.
I thought my table is too big to run, so I changed the limit and the DBMS time out, but it didn't work either. Can someone tell me what's the problem now?

I found the problem. Don't edit your MySQL database when you're connecting it with your Python Flask program. Edit means any CRUD actions.

Migrate existing database fields.E340 error on run

Hey everyone I'm fairly new to Python Anywhere, I'm running a django app on python 3.7, I've manually added the tables and fields I need via SSH in MySQL Workbench and ran [migrate.py inpectdb > /app/models.py] then makemigrations then when I run Migrate I get this:
ERRORS: auth.Group.permissions: (fields.E340) The field's intermediary table 'auth_group_permissions' clashes with the table name of 'app.AuthGroupPermissions'. auth.User.groups: (fields.E340) The field's intermediary table 'auth_user_groups' clashes with the table name of 'app.AuthUserGroups'. auth.User.user_permissions: (fields.E340) The field's intermediary table 'auth_user_user_permissions' clashes with the table name of 'app.AuthUserUserPermissions'.
If I remove the auth tables from the models.py and try to migrate I get:
File "/usr/lib/python3.7/site-packages/MySQLdb/connections.py", line 276, in query _mysql.connection.query(self, query) django.db.utils.OperationalError: (1071, 'Specified key was too long; max key length is 767 bytes')
From what I've read it is conflicting with the settings.py [INSTALLED_APPS] but I'm not sure where to go from here to get the migration to work properly.

The extra tables that you noticed were created by Django because you have the app that creates those tables enabled in your INSTALLED_APPS. From the table names involved, I'm guessing it's django.contrib.auth that's adding them. There are probably other tables that are being created that way, but they are just not clashing with the tables you've already created.
The second error you're getting is because you have tried to create a key on a column (or columns) that is too big to be a key. That may still be as a result of the auth_ tables clashing. For instance, the Django model may be specifying a key on the id of a table, expecting it to be an integer column, but your database has a large string column for id instead.
I suspect that you may continue to have issues as long as you try to get the Django database and your database to be in the same database. Django does, however, support multiple databases so you could put your legacy database in one database and have your Django database in another. That way, they have no way on stepping on each other.

in mysql table exists, but it doesn't [duplicate]

I am having the weirdest error of all.
Sometimes, when creating or altering tables, I get the 'table already exists' error. However, DROP TABLE returns '#1051 - unknown table'. So I got a table I cannot create, cannot drop.
When I try to drop the database, mysqld crashes. Sometimes it helps to create another db with different name, sometimes it does not.
I use a DB with ~50 tables, all InnoDB. This problem occurs with different tables.
I experienced this on Windows, Fedora and Ubuntu, MySQL 5.1 and 5.5. Same behaviour, when using PDO, PHPMyAdmin or commandline. I use MySQL Workbench to manage my schema - I saw some related errors (endlines and stuff), however none of them were relevant for me.
No, it is not a view, it is a table. All names are lowercase.
I tried everything I could google - flushing tables, moving .frm files from db to db, reading mysql log, nothing helped but reinstalling the whole damn thing.
'Show tables' reveals nothing, 'describe' table says 'table doesn't exist,' there is no .frm file, yet 'create table' still ends with an error (and so does 'create table if not exists') and dropping database crashes mysql
Related, yet unhelpful questions:
Mysql 1050 Error "Table already exists" when in fact, it does not
MySQL Table does not exist error, but it does exist
Edit:
mysql> use askyou;
Database changed
mysql> show tables;
Empty set (0.00 sec)
mysql> create table users_has_friends (id int primary key);
ERROR 1050 (42S01): Table '`askyou`.`users_has_friends`' already exists
mysql> drop table users_has_friends;
ERROR 1051 (42S02): Unknown table 'users_has_friends'
And such, all the same: table doesn't exist, yet cannot be created;
mysql> drop database askyou;
ERROR 2013 (HY000): Lost connection to MySQL server during query
Names change, this is not the only table / database I've run into problems with

I've seen this issue when the data file is missing in the data directory but the table definition file exists or vise-versa. If you're using innodb_file_per_table, check the data directory to make sure you have both an .frm file and .ibd file for the table in question. If it's MYISAM, there should be a .frm, .MYI and a .MYD file.
The problem can usually be resolved by deleting the orphaned file manually.

Going on a wild guess here, but it seems like innodb still has an entry for your tables in a tablespace, probably in ibdata. If you really don't need any of the data, or if you have backups, try the following:
Delete all schemas (excluding mysql)
shut down the database
Make sure that all folders in your data directory have been removed properly (again, excluding mysql)
delete ibdata and log files
restart the database. It should recreate the tablespace and logs from scratch.

The fix turns out to be easy; at least what I worked out, worked for me.
Create a table "zzz" on another MySQL instance, where zzz is the problem table name.
(i.e. if the table is called schrodinger, substitute that for zzz whever written.)
It does not matter what the definition of the table is. It's a temporary dummy;
Copy the zzz.frm file to the database directory on server where the table should be,
making sure file ownership and permissions are still correct on the file.
On MySQL, you can now do "show tables;", and the table zzz will be there.
mysql> drop table zzz;
...should now works. Clear any zzz.MYD or ZZZ.MYI files in the directory if necessary.

I doubt this is a direct answer to the question case here, but here is how I solved this exact perceived problem on my OS X Lion system.
I frequently create/drop tables for some analytics jobs I have scheduled. At some point, I started getting table already exists errors half-way through my script. A server restart typically solved the issue, but that was too annoying of a solution.
Then I noticed in the local error log file this particular line:
[Warning] Setting lower_case_table_names=2 because file system for /usr/local/mysql/data/ is case insensitive
This gave me the idea that maybe if my tables contained capital letters, MySQL would be fooled into thinking they are still there even after I had dropped them. That turned out to be the case and switching to using only lowercase letters for table names made the problem go away.
It is likely the result of some misconfiguration in my case, but hopefully this error case will help someone waste less time trying to find a solution.

This is an old question but I just hit the same issue and an answer in one of the related issues linked at the top was just what I needed and far less drastic than deleting files, tables, shutting down the server etc.
mysqladmin -uxxxxxx -pyyyyy flush-tables

If will are stock with this error 1051 and you only want to delete the database and import this again do this steps and all gonna be just fine....
in Unix envoriment AS root:
rm -rf /var/lib/mysql/YOUR_DATABASE;
OPTIONAL -> mysql_upgrade --force
mysqlcheck -uUSER -pPASS YOUR_DATABASE
mysqladmin -uUSER -pPASS drop YOUR_DATABASE
mysqladmin -uUSER -pPASS create YOUR_DATABASE
mysql -uUSER -pPASS YOUR_DATABASE < IMPORT_FILE
Regards,
Christus

In my case the problem was solved by changing the ownership of the mysql data directory to the user that ran the application. (In my case it was a Java application running Jetty webserver.)
Even though mysql was running and other apps could use it properly, this app had a problem with that. After changing the data directory ownership and resetting the user's password, everything worked properly.

I was having this problem with one particular table. Reading the possible solutions i've did some steps like:
Search for orphan files: didn't exist anyone;
execute: show full tables in database;: didn't see the problematic one;
execute: describe table;: returned table doesn't exist;
execute: SELECT * FROM information_schema.TABLES WHERE TABLE_NAME='table';: returned Empty set;
Search by the phpMyAdmin manually the query above: didn't exist;
And, after those steps, i check again with the show tables; and... vualá! the problematic table was gone. I could create it and drop it with the same problematic name with no problem, and i didn't have even to restart the server! Weird...

I had this problem and hoped deleting the IBD file would help as posted above but it made no difference . MySQL only recreated a new IBD file . In my case, there are actually similar tables in other databases in the same MySQL instance . Since the FRM file was missing , I copied the FRM file from the similar table in another database , restarted MySQL and the table worked correctly .

I ran into this error after I created a table and deleted it, then wanted to create it again.
In my case, I had a self-contained dump file so I dropped my schema, recreated it and imported tables and data using the dump file.

It happens at our site (but rarely) usually when an "event" happens while running certain scripts that do a lot of rebuilding. Events include network outages or power problems.
What I do for this on the very rare occasions it happens - I use the heavy-handed approach:
I needed to simply get rid-of-and-rebuild the particular table. I'm usually in a position that this is OK since the table is being built. (Your situation may be different if you need to recover data)
As an admin, go into the mysql installation (on windows its may be "...program files/mysql/MySQL Server xx/data/<schemaname>
Find the offending file with the table name in the <schemaname> folder - and delete it.
Check for orphaned temporary files and delete them too. #...frm files if they happen to be there.
MySQL will let you CREATE the table again
I've had this problem on a couple of different databases over a long time (years). It was a stumper because the contradicting messages. The first time I did a variation of the deleting/rebuilding/renaming database as described in the other answers and managed to get things going, but it definitely takes longer that way. Lucky for me it's always happened to reference tables that are being rebuilt - DROP'd and CREATEd - typically in the morning. Rarely got the problem but came to recognize it as a special quirky case. (I'll restate : if you need to recover the data look to the other solutions.)
it isn't a table belonging to another user, or in another database
it isn't the upper/lower case issue, I use all lower-case, but that was an interesting issue!
it was extra extra frustrating seeing responses with variations of "it definitely was <there/not-there/some-other-user-table-case> and you're just not doing it right" :)
the table didn't show on "show tables"
the table was (always was/had been) an INNODB table.
trying to DROP the table gave the error message that the table doesn't exist.
but trying to CREATE the table gave the error message that the table already exists.
using mysql 5.0 or 5.1
REPAIR is ineffective for this problem

How can I reset a 'ghost' table in MySQL? [duplicate]

I am having the weirdest error of all.
Sometimes, when creating or altering tables, I get the 'table already exists' error. However, DROP TABLE returns '#1051 - unknown table'. So I got a table I cannot create, cannot drop.
When I try to drop the database, mysqld crashes. Sometimes it helps to create another db with different name, sometimes it does not.
I use a DB with ~50 tables, all InnoDB. This problem occurs with different tables.
I experienced this on Windows, Fedora and Ubuntu, MySQL 5.1 and 5.5. Same behaviour, when using PDO, PHPMyAdmin or commandline. I use MySQL Workbench to manage my schema - I saw some related errors (endlines and stuff), however none of them were relevant for me.
No, it is not a view, it is a table. All names are lowercase.
I tried everything I could google - flushing tables, moving .frm files from db to db, reading mysql log, nothing helped but reinstalling the whole damn thing.
'Show tables' reveals nothing, 'describe' table says 'table doesn't exist,' there is no .frm file, yet 'create table' still ends with an error (and so does 'create table if not exists') and dropping database crashes mysql
Related, yet unhelpful questions:
Mysql 1050 Error "Table already exists" when in fact, it does not
MySQL Table does not exist error, but it does exist
Edit:
mysql> use askyou;
Database changed
mysql> show tables;
Empty set (0.00 sec)
mysql> create table users_has_friends (id int primary key);
ERROR 1050 (42S01): Table '`askyou`.`users_has_friends`' already exists
mysql> drop table users_has_friends;
ERROR 1051 (42S02): Unknown table 'users_has_friends'
And such, all the same: table doesn't exist, yet cannot be created;
mysql> drop database askyou;
ERROR 2013 (HY000): Lost connection to MySQL server during query
Names change, this is not the only table / database I've run into problems with

I've seen this issue when the data file is missing in the data directory but the table definition file exists or vise-versa. If you're using innodb_file_per_table, check the data directory to make sure you have both an .frm file and .ibd file for the table in question. If it's MYISAM, there should be a .frm, .MYI and a .MYD file.
The problem can usually be resolved by deleting the orphaned file manually.

Going on a wild guess here, but it seems like innodb still has an entry for your tables in a tablespace, probably in ibdata. If you really don't need any of the data, or if you have backups, try the following:
Delete all schemas (excluding mysql)
shut down the database
Make sure that all folders in your data directory have been removed properly (again, excluding mysql)
delete ibdata and log files
restart the database. It should recreate the tablespace and logs from scratch.

The fix turns out to be easy; at least what I worked out, worked for me.
Create a table "zzz" on another MySQL instance, where zzz is the problem table name.
(i.e. if the table is called schrodinger, substitute that for zzz whever written.)
It does not matter what the definition of the table is. It's a temporary dummy;
Copy the zzz.frm file to the database directory on server where the table should be,
making sure file ownership and permissions are still correct on the file.
On MySQL, you can now do "show tables;", and the table zzz will be there.
mysql> drop table zzz;
...should now works. Clear any zzz.MYD or ZZZ.MYI files in the directory if necessary.

I doubt this is a direct answer to the question case here, but here is how I solved this exact perceived problem on my OS X Lion system.
I frequently create/drop tables for some analytics jobs I have scheduled. At some point, I started getting table already exists errors half-way through my script. A server restart typically solved the issue, but that was too annoying of a solution.
Then I noticed in the local error log file this particular line:
[Warning] Setting lower_case_table_names=2 because file system for /usr/local/mysql/data/ is case insensitive
This gave me the idea that maybe if my tables contained capital letters, MySQL would be fooled into thinking they are still there even after I had dropped them. That turned out to be the case and switching to using only lowercase letters for table names made the problem go away.
It is likely the result of some misconfiguration in my case, but hopefully this error case will help someone waste less time trying to find a solution.

This is an old question but I just hit the same issue and an answer in one of the related issues linked at the top was just what I needed and far less drastic than deleting files, tables, shutting down the server etc.
mysqladmin -uxxxxxx -pyyyyy flush-tables

If will are stock with this error 1051 and you only want to delete the database and import this again do this steps and all gonna be just fine....
in Unix envoriment AS root:
rm -rf /var/lib/mysql/YOUR_DATABASE;
OPTIONAL -> mysql_upgrade --force
mysqlcheck -uUSER -pPASS YOUR_DATABASE
mysqladmin -uUSER -pPASS drop YOUR_DATABASE
mysqladmin -uUSER -pPASS create YOUR_DATABASE
mysql -uUSER -pPASS YOUR_DATABASE < IMPORT_FILE
Regards,
Christus

In my case the problem was solved by changing the ownership of the mysql data directory to the user that ran the application. (In my case it was a Java application running Jetty webserver.)
Even though mysql was running and other apps could use it properly, this app had a problem with that. After changing the data directory ownership and resetting the user's password, everything worked properly.

I was having this problem with one particular table. Reading the possible solutions i've did some steps like:
Search for orphan files: didn't exist anyone;
execute: show full tables in database;: didn't see the problematic one;
execute: describe table;: returned table doesn't exist;
execute: SELECT * FROM information_schema.TABLES WHERE TABLE_NAME='table';: returned Empty set;
Search by the phpMyAdmin manually the query above: didn't exist;
And, after those steps, i check again with the show tables; and... vualá! the problematic table was gone. I could create it and drop it with the same problematic name with no problem, and i didn't have even to restart the server! Weird...

I had this problem and hoped deleting the IBD file would help as posted above but it made no difference . MySQL only recreated a new IBD file . In my case, there are actually similar tables in other databases in the same MySQL instance . Since the FRM file was missing , I copied the FRM file from the similar table in another database , restarted MySQL and the table worked correctly .

I ran into this error after I created a table and deleted it, then wanted to create it again.
In my case, I had a self-contained dump file so I dropped my schema, recreated it and imported tables and data using the dump file.

It happens at our site (but rarely) usually when an "event" happens while running certain scripts that do a lot of rebuilding. Events include network outages or power problems.
What I do for this on the very rare occasions it happens - I use the heavy-handed approach:
I needed to simply get rid-of-and-rebuild the particular table. I'm usually in a position that this is OK since the table is being built. (Your situation may be different if you need to recover data)
As an admin, go into the mysql installation (on windows its may be "...program files/mysql/MySQL Server xx/data/<schemaname>
Find the offending file with the table name in the <schemaname> folder - and delete it.
Check for orphaned temporary files and delete them too. #...frm files if they happen to be there.
MySQL will let you CREATE the table again
I've had this problem on a couple of different databases over a long time (years). It was a stumper because the contradicting messages. The first time I did a variation of the deleting/rebuilding/renaming database as described in the other answers and managed to get things going, but it definitely takes longer that way. Lucky for me it's always happened to reference tables that are being rebuilt - DROP'd and CREATEd - typically in the morning. Rarely got the problem but came to recognize it as a special quirky case. (I'll restate : if you need to recover the data look to the other solutions.)
it isn't a table belonging to another user, or in another database
it isn't the upper/lower case issue, I use all lower-case, but that was an interesting issue!
it was extra extra frustrating seeing responses with variations of "it definitely was <there/not-there/some-other-user-table-case> and you're just not doing it right" :)
the table didn't show on "show tables"
the table was (always was/had been) an INNODB table.
trying to DROP the table gave the error message that the table doesn't exist.
but trying to CREATE the table gave the error message that the table already exists.
using mysql 5.0 or 5.1
REPAIR is ineffective for this problem

Schrödingers MySQL table: exists, yet it does not

I am having the weirdest error of all.
Sometimes, when creating or altering tables, I get the 'table already exists' error. However, DROP TABLE returns '#1051 - unknown table'. So I got a table I cannot create, cannot drop.
When I try to drop the database, mysqld crashes. Sometimes it helps to create another db with different name, sometimes it does not.
I use a DB with ~50 tables, all InnoDB. This problem occurs with different tables.
I experienced this on Windows, Fedora and Ubuntu, MySQL 5.1 and 5.5. Same behaviour, when using PDO, PHPMyAdmin or commandline. I use MySQL Workbench to manage my schema - I saw some related errors (endlines and stuff), however none of them were relevant for me.
No, it is not a view, it is a table. All names are lowercase.
I tried everything I could google - flushing tables, moving .frm files from db to db, reading mysql log, nothing helped but reinstalling the whole damn thing.
'Show tables' reveals nothing, 'describe' table says 'table doesn't exist,' there is no .frm file, yet 'create table' still ends with an error (and so does 'create table if not exists') and dropping database crashes mysql
Related, yet unhelpful questions:
Mysql 1050 Error "Table already exists" when in fact, it does not
MySQL Table does not exist error, but it does exist
Edit:
mysql> use askyou;
Database changed
mysql> show tables;
Empty set (0.00 sec)
mysql> create table users_has_friends (id int primary key);
ERROR 1050 (42S01): Table '`askyou`.`users_has_friends`' already exists
mysql> drop table users_has_friends;
ERROR 1051 (42S02): Unknown table 'users_has_friends'
And such, all the same: table doesn't exist, yet cannot be created;
mysql> drop database askyou;
ERROR 2013 (HY000): Lost connection to MySQL server during query
Names change, this is not the only table / database I've run into problems with

I've seen this issue when the data file is missing in the data directory but the table definition file exists or vise-versa. If you're using innodb_file_per_table, check the data directory to make sure you have both an .frm file and .ibd file for the table in question. If it's MYISAM, there should be a .frm, .MYI and a .MYD file.
The problem can usually be resolved by deleting the orphaned file manually.

Going on a wild guess here, but it seems like innodb still has an entry for your tables in a tablespace, probably in ibdata. If you really don't need any of the data, or if you have backups, try the following:
Delete all schemas (excluding mysql)
shut down the database
Make sure that all folders in your data directory have been removed properly (again, excluding mysql)
delete ibdata and log files
restart the database. It should recreate the tablespace and logs from scratch.

The fix turns out to be easy; at least what I worked out, worked for me.
Create a table "zzz" on another MySQL instance, where zzz is the problem table name.
(i.e. if the table is called schrodinger, substitute that for zzz whever written.)
It does not matter what the definition of the table is. It's a temporary dummy;
Copy the zzz.frm file to the database directory on server where the table should be,
making sure file ownership and permissions are still correct on the file.
On MySQL, you can now do "show tables;", and the table zzz will be there.
mysql> drop table zzz;
...should now works. Clear any zzz.MYD or ZZZ.MYI files in the directory if necessary.

I doubt this is a direct answer to the question case here, but here is how I solved this exact perceived problem on my OS X Lion system.
I frequently create/drop tables for some analytics jobs I have scheduled. At some point, I started getting table already exists errors half-way through my script. A server restart typically solved the issue, but that was too annoying of a solution.
Then I noticed in the local error log file this particular line:
[Warning] Setting lower_case_table_names=2 because file system for /usr/local/mysql/data/ is case insensitive
This gave me the idea that maybe if my tables contained capital letters, MySQL would be fooled into thinking they are still there even after I had dropped them. That turned out to be the case and switching to using only lowercase letters for table names made the problem go away.
It is likely the result of some misconfiguration in my case, but hopefully this error case will help someone waste less time trying to find a solution.

This is an old question but I just hit the same issue and an answer in one of the related issues linked at the top was just what I needed and far less drastic than deleting files, tables, shutting down the server etc.
mysqladmin -uxxxxxx -pyyyyy flush-tables

If will are stock with this error 1051 and you only want to delete the database and import this again do this steps and all gonna be just fine....
in Unix envoriment AS root:
rm -rf /var/lib/mysql/YOUR_DATABASE;
OPTIONAL -> mysql_upgrade --force
mysqlcheck -uUSER -pPASS YOUR_DATABASE
mysqladmin -uUSER -pPASS drop YOUR_DATABASE
mysqladmin -uUSER -pPASS create YOUR_DATABASE
mysql -uUSER -pPASS YOUR_DATABASE < IMPORT_FILE
Regards,
Christus

In my case the problem was solved by changing the ownership of the mysql data directory to the user that ran the application. (In my case it was a Java application running Jetty webserver.)
Even though mysql was running and other apps could use it properly, this app had a problem with that. After changing the data directory ownership and resetting the user's password, everything worked properly.

I was having this problem with one particular table. Reading the possible solutions i've did some steps like:
Search for orphan files: didn't exist anyone;
execute: show full tables in database;: didn't see the problematic one;
execute: describe table;: returned table doesn't exist;
execute: SELECT * FROM information_schema.TABLES WHERE TABLE_NAME='table';: returned Empty set;
Search by the phpMyAdmin manually the query above: didn't exist;
And, after those steps, i check again with the show tables; and... vualá! the problematic table was gone. I could create it and drop it with the same problematic name with no problem, and i didn't have even to restart the server! Weird...

I had this problem and hoped deleting the IBD file would help as posted above but it made no difference . MySQL only recreated a new IBD file . In my case, there are actually similar tables in other databases in the same MySQL instance . Since the FRM file was missing , I copied the FRM file from the similar table in another database , restarted MySQL and the table worked correctly .

I ran into this error after I created a table and deleted it, then wanted to create it again.
In my case, I had a self-contained dump file so I dropped my schema, recreated it and imported tables and data using the dump file.

It happens at our site (but rarely) usually when an "event" happens while running certain scripts that do a lot of rebuilding. Events include network outages or power problems.
What I do for this on the very rare occasions it happens - I use the heavy-handed approach:
I needed to simply get rid-of-and-rebuild the particular table. I'm usually in a position that this is OK since the table is being built. (Your situation may be different if you need to recover data)
As an admin, go into the mysql installation (on windows its may be "...program files/mysql/MySQL Server xx/data/<schemaname>
Find the offending file with the table name in the <schemaname> folder - and delete it.
Check for orphaned temporary files and delete them too. #...frm files if they happen to be there.
MySQL will let you CREATE the table again
I've had this problem on a couple of different databases over a long time (years). It was a stumper because the contradicting messages. The first time I did a variation of the deleting/rebuilding/renaming database as described in the other answers and managed to get things going, but it definitely takes longer that way. Lucky for me it's always happened to reference tables that are being rebuilt - DROP'd and CREATEd - typically in the morning. Rarely got the problem but came to recognize it as a special quirky case. (I'll restate : if you need to recover the data look to the other solutions.)
it isn't a table belonging to another user, or in another database
it isn't the upper/lower case issue, I use all lower-case, but that was an interesting issue!
it was extra extra frustrating seeing responses with variations of "it definitely was <there/not-there/some-other-user-table-case> and you're just not doing it right" :)
the table didn't show on "show tables"
the table was (always was/had been) an INNODB table.
trying to DROP the table gave the error message that the table doesn't exist.
but trying to CREATE the table gave the error message that the table already exists.
using mysql 5.0 or 5.1
REPAIR is ineffective for this problem