CODEWITHSUNDEEP
mysqlsql
Alexander Bösecke
Alexander Bösecke

Reputation: 83

Use a variable or function in MYSQLs ALTER TABLE statement

In Mysql/MariaDB I like to set the comment of an existing column to a string containing the current date.

But I only get SQL syntax errors. I've tried so far:

SELECT @date := CONCAT('saved at', now());
ALTER TABLE table_name MODIFY 
    column_name <complete column definition> COMMENT @date;

Also not working:

ALTER TABLE table_name MODIFY
    column_name <complete column definition> COMMENT now();

Of course this works:

ALTER TABLE table_name MODIFY
    column_name <complete column definition> COMMENT 'saved at today';

Is this possible without an external script?

Upvotes: 0

Views: 309

Answers (1)

Akina
Akina

Reputation: 42622

SET @sql := CONCAT ( 'ALTER TABLE {table_name} ',
                     'MODIFY {column_name} {complete column definition} ',
                     'COMMENT \'saved at ' , CURRENT_TIMESTAMP, '\'' );
PREPARE stmt FROM @sql;
EXECUTE stmt;
DROP PREPARE stmt;

demo

Upvotes: 2

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