I'm new to sql and trying to get to grips with some of the basics.
Say I've created a database as follows:
create database mydatabase;
and I want to back this up to a dump file. My confusion comes in here - what is this dump file? Does this automatically generate when I run the mysqldump command? Do I have to create it beforehand? If so, how? Sorry if this comes off stupid but I'm just lost here.
I know the final command would look as follows:
mysqldump -u -p mydatabase > SOMETHING;
but I don't know what to actually insert as the something
The dump file is just a file usually with a bunch of scripts you can run to recreate something in the database. Different database system have their own way of generating these, but you could effectively take a dump from an mysql database and into another rdbms as long as the scripts are compatible.
There are different options;
You could create a dump of just the schema. So that you can recreate that database later on without the data.
Create the dump with schema and data. So that you can recreate the scheme as well as the data within it.
Create the dump with just the data. So you can run those insert commands against another database of the same schema.
Basically dumps are just a way to get back to a previous state. They come in handy for different situation. Such as backing up data, replicating a data from one database to another.
As for the commands I have not used mysql in a while but looks like you are on the right track.
I have a mysql database with lots of tables and records in it. I want to get the list of queries which were used to create tables , insert records etc in that mysqldb. Is it possible. I have seen it in Oracle sql developer. If we click on the table we can view the queries which we have used, for DDL. How to do that in msyql. I am using mysql command line client.
You could use the mysqldump-utility for that
In Linux:
mysqldump my_database_name >dumpfile.sql
I have a large database, "devDB" that I want to duplicate on the same server to become my live database, "liveDB". Can I make a duplicate without using mysqldump? Last time I used mysqldump it took a really long time. Seems like there could be a quicker way if its just a matter of copying the files. Can you create a new database and copy all the tables?
If you don't want to use mysqldump, create you databases/schema,
and copy the tables from one DB to the other:
CREATE TABLE `liveDB.sample_table` SELECT * FROM `devDB.sample_table`;
Michael's answer above is a good idea if you want to put the newDB in the same MySQL instance as devDB. If you want to put liveDB on a separate Instance, you could use mysqldump to "pipe" the output directly into the "source" of liveDB, so that you could avoid Disk I/O. Also to improve performance, you could disable MySQL's binlog on the target DB while Inserting data.
I have 2 active database connections, I need to replace a number of tables from 'connection1' with that of connection2. The structures may, or may not be same, (depending if we make changes to the connection1 table.
I would assume I should do a complete table dump and replace keys where neccesary, but I really have no idea how to do this :)
Any help?
Have a look at Schema and Data sync tools in dbForge Studio for MySQL. It will help you to compare two databases on different servers, map tables and fields, generate and run synchronization script.
I ended up using the build in system command in PHP and mysqldump to first dump the data (export) to a file, then used system() again with mysql to import it into the new table and replace the old one.
Works like a charm :)
If I have a MySQL database with several tables on a live server, now I would like to migrate this database to another server. Of course, the migration I mean here involves some database tables, for example: add some new columns to several tables, add some new tables etc..
Now, the only method I can think of is to use some php/python(two scripts I know) script, connect two databases, dump the data from the old database, and then write into the new database. However, this method is not efficient at all. For example: in old database, table A has 28 columns; in new database, table A has 29 columns, but the extra column will have default value 0 for all the old rows. My script still needs to dump the data row by row and insert each row into the new database.
Using MySQLDump etc.. won't work. Here is the detail. For example: I have FOUR old databases, I can name them as 'DB_a', 'DB_b', 'DB_c', 'DB_d'. Now the old table A has 28 columns, I want to add each row in table A into the new database with a new column ID 'DB_x' (x to indicate which database it comes from). If I can't differentiate the database ID by the row's content, the only way I can identify them is going through some user input parameters.
Is there any tools or a better method than writing a script yourself? Here, I dont need to worry about multithread writing problems etc.., I mean the old database will be down (not open to public usage etc.., only for upgrade ) for a while.
Thanks!!
I don't entirely understand your situation with the columns (wouldn't it be more sensible to add any new columns after migration?), but one of the arguably fastest methods to copy a database across servers is mysqlhotcopy. It can copy myISAM only and has a number of other requirements, but it's awfully fast because it skips the create dump / import dump step completely.
Generally when you migrate a database to new servers, you don't apply a bunch of schema changes at the same time, for the reasons that you're running into right now.
MySQL has a dump tool called mysqldump that can be used to easily take a snapshot/backup of a database. The snapshot can then be copied to a new server and installed.
You should figure out all the changes that have been done to your "new" database, and write out a script of all the SQL commands needed to "upgrade" the old database to the new version that you're using (e.g. ALTER TABLE a ADD COLUMN x, etc). After you're sure it's working, take a dump of the old one, copy it over, install it, and then apply your change script.
Use mysqldump to dump the data, then echo output.txt > msyql. Now the old data is on the new server. Manipulate as necessary.
Sure there are tools that can help you achieving what you're trying to do. Mysqldump is a premier example of such tools. Just take a glance here:
http://dev.mysql.com/doc/refman/5.1/en/mysqldump.html
What you could do is:
1) You make a dump of the current db, using mysqldump (with the --no-data option) to fetch the schema only
2) You alter the schema you have dumped, adding new columns
3) You create your new schema (mysql < dump.sql - just google for mysql backup restore for more help on the syntax)
4) Dump your data using the mysqldump complete-insert option (see link above)
5) Import your data, using mysql < data.sql
This should do the job for you, good luck!
Adding extra rows can be done on a live database:
ALTER TABLE [table-name] ADD [row-name] MEDIUMINT(8) default 0;
MySql will default all existing rows to the default value.
So here is what I would do:
make a copy of you're old database with MySql dump command.
run the resulting SQL file against you're new database, now you have an exact copy.
write a migration.sql file that will modify you're database with modify table commands and for complex conversions some temporary MySql procedures.
test you're script (when fail, go to (2)).
If all OK, then goto (1) and go live with you're new database.
These are all valid approaches, but I believe you want to write a sql statement that writes other insert statements that support the new columns you have.