MySQL存储过程更改多表结构

Question

I'm building a small script as a function or a stored procedure to be able to alter a table structure only in tables that has no column named 'address'.

If the table doesn't have the column address then the script will add it:

ALTER TABLE XXXX ADD COLUMN address VARCHAR(150) NULL after command;

So far I have found the way to access to the tables list that HAS the column 'address' on its structure by querying the information_schema.COLUMNS table; such thing is not what I need because I need exactly the opposite, which is tables list that has not the column named 'address' on its structure.

so basically is a script that needs to do something like this:

ALTER TABLE 
(SELECT TABLE_NAME FROM information_schema.COLUMNS WHERE TABLE_SCHEMA = 'mydatabase' 
AND TABLE_NAME LIKE 'mytable_%' AND COLUMN_NAME = 'address') 
ADD COLUMN IF NOT EXISTS address  VARCHAR(150) NULL after command;

Something like that is what I need, it needs the validation of column name address and it will attempt to add the column only if it does not exists, otherwise it will return an exception and the query will die.

PHP or any other programming language cannot be used because more than 4000 tables will be upgraded and the http request will die before the database finish the operations.

Another possibility is to just handle the exception in case of the existence of the column named 'address' something to be able to continue the operations no matter if the exception returns, something that just continue with the query execution so the tables without exceptions will be updated....

Answer 1

You will have to build dynamic SQL for this. The best bet is to do this

OOTOMH code

Select 'Alter table ' + TableName ' + Add Address VarChar (150)'
From Information_schema.Tables T
Where Not Exists
(
Select 1
From Information_schema.Columns C
Where C.TableName = T.TableName
And C.ColumnName = 'Address'
)

Now that you have generated the code, you can execute it by hand.

If this isn't really something you do on a daily basis, then there isn't much of a need to deploy the Stored Proc, is there?

If you really really want it, then you have a plethora of options - add the string to a variable, loop through the set with a cursor, etc.