I cannot change the column name in a mysql database I created.
I have tried the following commands, and none of them appear to work.
alter table (mytablename) CHANGE COLUMN (oldcolumnname) (newcolumnname) varchar(120);
alter table (mytablename) RENAME COLUMN (oldcolumnname) (newcolumnname) varchar(120);
ALTER TABLE (mytablename) CHANGE (oldcolumnname) (newcolumnname) varchar(120);
Where (mytablename) is the name of the table that I created, (oldcolumnname) is the original column name, and (newcolumnname) is the new column name.
This is a simple to-do list I created to learn MySQL with the following items:
id
todo
completed
1
Prepare for Take Off
Yes
2
Learn some MySQL
Yes
3
Remember that damn semicolon
No
In this case, I am trying to alter the column 'todo' to say either 'To Do' or 'To-Do' but every time I try these commands. I keep getting the famous "Check your SQL version manual".
Any hints as to what I might be doing wrong? TIA!
I have reviewed multiple tutorial websites and even reviewed another StackOverflow question
UPDATE
The ultimate solution was two-fold. First, I needed to use the TO phrase between the column names. Second, the column names do not like special characters.
The query that ultimately worked was:
ALTER TABLE mytablename CHANGE COLUMN todo TO ToDo
You should keep the column named todo; you can always change the output when you select like:
select id, todo as 'To Do', completed from ...
If you feel you really must include a space or - in the column name, in mysql you can use arbitrary identifiers that have not-usually allowed characters by enclosing them in backticks:
alter table ... rename column todo to `To Do`
but then every time you reference the column in sql you will need to enclose it in backticks:
select id,`To Do`,completed from ... where `To Do` like '%learn%'
Related
I currently have a MariaDB database with columns named after dates : 20200105, 20200914 etc.
If I try to add a column using ALTER TABLE dates ADD COLUMN IF NOT EXISTS (test VARCHAR(255));, it works and the test column is created.
If I type ALTER TABLE dates ADD COLUMN IF NOT EXISTS (20201205 VARCHAR(255));, though (so, with a number replacing "test"), the creation does not work anymore and MariaDB tells me that there is an error with my SQL syntax.
I have tried to put quotes around the column name, but that does not work (not even with "test").
Is there something obvious I am missing ?
Use backticks to escape the column name:
ALTER TABLE dates ADD COLUMN IF NOT EXISTS (`20201205` VARCHAR(255));
But really best practice frowns upon the use of naming your database objects with mandatory backticks. The reason for using a name like 20201205 as a column name is that you will forever be needing to escape it using backticks. Also, from a data design point of view, your data should grow with new dates in terms of increasing the number of records, not columns.
I have created a table and I wish to make a Computed Column from the concatenated values of three other fields in the table.
I want this Computed Field to take place at INSERT or UPDATE, so I am specifying PERSISTENT
I have tried the following code (in various ways) in phpMyAdmin but always get errors, which seem to be referencing immediately after ALTER table
I did not see a way of doing this when adding the field in phpMyAdmin, so I hoped I could ALTER it.
Alter TABLE 'tlImages'
CHANGE COLUMN tlImageQuery
AS CONCAT(tlImgTitle,"~",tlImgDescrip,"~",tlImgWhereWhen) PERSISTENT;
MariaDB version 10.0.29-MariaDB-cll-lve - MariaDB Server
phpMyAdmin . Version information: 4.0.10.18
First, lose single quotes around the table name, they are not suitable for this purpose. Use backticks or nothing.
You will still get a syntax error further in the statement, because AS clause should be in brackets. Add them.
You will still get a syntax error because you are missing column type before the AS (...) clause, add it.
You will still get a syntax error because CHANGE COLUMN needs two column names, old and new, use MODIFY instead.
Alter TABLE `tlImages`
MODIFY COLUMN tlImageQuery VARCHAR(128)
AS (CONCAT(tlImgTitle,"~",tlImgDescrip,"~",tlImgWhereWhen)) PERSISTENT
;
(Type VARCHAR(128) is given just as an example).
I have two tables called HRData and HRDataHistory. HRDataHistory has the same structure as HRData except the first column is an autoincrement field and the last column is a DateTime field.
HRData has a trigger:
CREATE TRIGGER [HR].[HRData_History]
ON [HR].[HRData]
AFTER INSERT, UPDATE
AS
INSERT INTO HR.HRDataHistory
SELECT *, GETDATE()
FROM inserted
;
GO
This is working on an existing development machine. I am trying to mirror this relationship on my local sql server instance so that I can test some changes. Using SSMS I used 'Script Table as Create To...' and created the structure of each table and index on my local sql server instance. However when I do this for the trigger I get the following error:
An explicit value for the identity column in table 'HR.HRDataHistory' can only be specified when a column list is used and IDENTITY_INSERT is ON.
I know the preferred method would be to specify the columns, but I want to mirror production which does not currently do that and further I want to understand why it is working in production but not on my test database.
You're getting this error because you're trying to insert data into an IDENTITY column, which auto-populates itself whenever you insert another row in that table.
Off the top of my head, you can do something like below (although I believe there are more elegant solutions and I do not guarantee that this is a safe solution, nor have I tried something like this and I recommend testing on a TEST database before trying in production/LIVE):
add another column to HRDataHistory table which does not have identity set on it (because you cannot remove identity form a colum once set), but must have the same datatype as the current ID (IDENTITY) column
use a UPDATE query to move all of your ID's from your IDENTITY column to your new column:
UPDATE HRDataHistory
SET new_column = ID
Drop the IDENTITY column (but this might have grave implications if you have any FK set on it and possibly other objects that use it):
ALTER TABLE HRDataHistory
DROP COLUMN ID
Rename the "new_column" to the name of your previous IDENTITY column:
EXEC sp_RENAME 'HRDataHistory.new_column' , 'ID', 'COLUMN'
At this point I believe you can use your trigger to "copy" the newly inserted data from the HRData table into the HRDataHistory, since the column names should match and there is no more conflict due to IDENTITY.
Again, this might (not guaranteed) work so I recommend you first check on a TEST environment.
I have a SQL database with a table inside called members and inside that there are some columns, one being an ID which auto-increments.
However I have done a few tests, and the auto-increment does work. But even after deleting the tests the auto-increment will not start from 0 again.
How do I make it will start back from 0 rather than carry on from about 17 or something...
EDIT:
I have worked out the answer:
In the "Operations" tab in phpMyAdmin there is a section called Table Options.
In there you can edit where the auto-increment continues from.
Assuming You're using MySQL:
To reset the next value of *auto_increment* column, you need to use ALTER TABLE statement in the following form:
ALTER TABLE my_table AUTO_INCREMENT=123
(Where "123" is the new next value)
If u are using postgresql u have following sql statement to alter sequence
ALTER SEQUENCE table_name_id_seq RESTART WITH 1
for example, if u have table called users, then u should do
ALTER SEQUENCE users_id_seq RESTART WITH 1
where 1 is the new sequence.
After importing an Excel table that contained some special characters (like carriage returns or line feeds) in the headers row, it seems that the phpMyAdmin utility handled this situation silently by inserting those chars in the field's name.
The problem arose later when I tried to import the table into other environments/tools like data integrators, etc. For example, the column "Date Start" was imported into the table as "Date\nStart", with a LINE FEED in the middle.
The field rename operation through phpMyAdmin fails with this error:
**\#1054 - Unknown column 'Date Start' in 'mytable'**
The obvious workaround would be to edit the original Excel file by hand (removing LF's) then reimporting the table in MySql as before, but I'm in the position of needing to refresh the schema while preserving the data in the table.
Next I tried this from an SQL panel in phpMyAdmin (note the \n in the field name, VARCHAR(16) is just an example, DATETIME or INT should work as well):
ALTER TABLE mytable CHANGE `Date\nStart` `Date Start` VARCHAR(16)
but again it gives error #1054 - Unknown column 'Date\nStart' in 'mytable'
I also checked the INFORMATION_SCHEMA db, but as #Steve stated below, it's a read-only database.
I'm using MySql 5.5.32 and phpMyAdmin 4.0.4.1 with a Win7 desktop. Any suggestions?
First of all, by reading the MySql manual you can appreciate (or hate) the extreme flexibility allowed by the naming rules, details on the special characters that are/aren't allowed in a table and column names can be found in this manual page:
https://dev.mysql.com/doc/refman/5.5/en/identifiers.html
After several attempts escaping the CR character I've found a solution that works from the phpMyAdmin SQL pane, I think it should work on command-line sessions as well (didn't try that).
In case you inadvertently created or imported columns with CR's in the name, it is possible to fix it by typing the ENTER key within the column name, inside the SQL ALTER TABLE statement (you MUST enclose names in backticks for this trick to work).
Example: To replace the unwanted 'Date\nStart' column name with 'Date Start' you should type this (please note, the CR/Enter at the end of the first line!):
ALTER TABLE mybuggytable CHANGE `Date
Start` `Date Start` VARCHAR(16)
As explained above, you can spot columns with CR's embedded with this statement:
USE INFORMATION_SCHEMA; SELECT * FROM COLUMNS WHERE COLUMN_NAME like '%\n%'
I typed the ALTER TABLE command in the my phpMyAdmin SQL pane, and it just worked fine.
I thought you couldn't write to INFORMATION_SCHEMA because of a permission issue, but after reading the MySQL Manual I realise this is expected behavior as the manual states:
Although you can select INFORMATION_SCHEMA as the default database with a USE statement, you can only read the contents of tables, not perform INSERT, UPDATE, or DELETE operations on them.
To achieve a table rename by using the RENAME TABLE command, first run a select query to find all the tables that need changing and then rename them replacing the carnage return with a space character.
To rename just a column from within a table the ALTER TABLE command can be used with the CHANGE COLUMN parameters, for example:
ALTER TABLE table_name CHANGE COLUMN 'Date\nStart' 'Date Start' DATETIME
I know you've already said that is the command you need, so I've tested this myself by firstly selecting the tables and then running the ALTER TABLE command and it worked fine. I was using the command line interface, so maybe the problem lies with phpMyAdmin - can you confirm it isn't encoding or escaping \n?
Here is what I tested via the command line and worked OK:
SELECT COLUMN_NAME
FROM `INFORMATION_SCHEMA`.`COLUMNS`
WHERE TABLE_SCHEMA = 'test_345'
AND TABLE_NAME LIKE '%\n%';
ALTER TABLE test_table1 CHANGE COLUMN 'Date\nStart' 'Date Start' DATETIME;
Either of these could be wrapped up into a routine should you think this would be useful in the future.