How to insert columns at a specific position in existing table?

sql

database-management

table-operations

column-positioning

byAnton Shumikhin·Feb 18, 2025

Positioning columns in tables isn't always straightforward due to DBMS constraints. When required, however, you can recreate the table and ensure the column order suits your needs:

-- Create new structure with space for more snacks
CREATE TABLE new_table AS
SELECT col1, /* pops in an extra slice of data */
'default_value' AS new_col, col2, col3 FROM old_table;

-- Swap the old snacks with the new. Munching can continue!
DROP TABLE old_table;
ALTER TABLE new_table RENAME TO old_table;

Remember to preserve your data and constraints. Modify 'default_value' and datatype for new_col as you desire.

Sneaky tactics and exhaustive methods

Calling in the cavalry: MySQL to the Rescue!

In MySQL, you can employ the AFTER keyword with ALTER TABLE, inserting columns with the precision of an apache helicopter landing:

ALTER TABLE table_name
ADD COLUMN new_column_name data_type AFTER existing_column_name;
-- Now you see it, now it's there!

Musical chairs without leaving the room: Reordering columns

Reshuffle columns without additions using CHANGE or MODIFY with FIRST or AFTER. No one will notice, we assure you.

The not-so-welcome guests: Non-nullable columns

When adding a new column that can't be null, remember to roll out the red carpet with a default value or update every row, so no one feels left out.

(Sorry PostgreSQL fans!) Unsupported column positioning

Some DBMS, like PostgreSQL, don't support Dwight Schrute's level of orderliness (column positioning). Here we need a Plan B: modify your application logic to work with this limitation.

Troubleshooting guide and hacker tips

Honoring tradition: Constraints and defaults

When rebuilding tables (painting over your Da Vinci), take care of the layouts and textures: primary keys, indexes, foreign keys, and default values.

The giant's wrath: Handling large datasets

Addition operations can, at times, be as slow as a turtle on a skateboard, especially with large datasets. Be ready for a Quickie Mart marathon, and ensure your application doesn't shut down in frustration.

Mirror Check: Verifying column position and integrity

Check your hair and your code. Dispatch a swift SELECT * FROM table_name LIMIT 0 to confirm your new column's position and maintain the table's structural integrity.

Robot takeover: Automating and script generation

Here, our robotic mates come in handy. Using scripts to manage migration can be a lifesaver. Automate for your sanity; imagine the fun it could add to Friday night parties.

explain-codes / Sql / How to insert columns at a specific position in existing table?

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