MySQL 如果mysql中存在列，如何删除？
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时间：2020-08-31 22:02:17 来源:igfitidea点击:
how to drop a column if exists in mysql?
提问by CloudSeph
ALTER TABLE user DROP COLUMN registered_date
We can drop a column using the above command. But how can i drop it only if the column registered_date exist?
我们可以使用上面的命令删除一列。但是，只有当列registered_date 存在时，我才能删除它吗？
回答by Jibin Balachandran
IF EXISTS(SELECT *
FROM information_schema.COLUMNS
WHERE
TABLE_SCHEMA = 'db_name'
AND TABLE_NAME = 'table_name'
AND COLUMN_NAME = 'column_name')
BEGIN
ALTER TABLE table_name DROP COLUMN column_name
END
OR
或者
IF (SELECT COUNT(*)
FROM information_schema.COLUMNS
WHERE
TABLE_SCHEMA = 'db_name'
AND TABLE_NAME = 'table_name'
AND COLUMN_NAME = 'column_name'>0)
BEGIN
ALTER TABLE table_name DROP COLUMN column_name
END
