Mysql – How to remove constraints from the MySQL table

alterconstraintsforeign-keysMySQL

I want to remove constraints from my table. My query is:

ALTER TABLE `tbl_magazine_issue` 
DROP CONSTRAINT `FK_tbl_magazine_issue_mst_users`

But I got an error:

#1064 – You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'constraint FK_tbl_magazine_issue_mst_users' at line 1

Best Answer

Mysql has a special syntax for dropping foreign key constraints:

ALTER TABLE tbl_magazine_issue
  DROP FOREIGN KEY FK_tbl_magazine_issue_mst_users

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Mysql – Should I use the datetime or timestamp data type in MySQL

Timestamps in MySQL are generally used to track changes to records, and are often updated every time the record is changed. If you want to store a specific value you should use a datetime field.

If you meant that you want to decide between using a UNIX timestamp or a native MySQL datetime field, go with the native format. You can do calculations within MySQL that way ("SELECT DATE_ADD(my_datetime, INTERVAL 1 DAY)") and it is simple to change the format of the value to a UNIX timestamp ("SELECT UNIX_TIMESTAMP(my_datetime)") when you query the record if you want to operate on it with PHP.

Mysql – How to get the max of two values in MySQL

Use GREATEST()

E.g.:

SELECT GREATEST(2,1);

Note: Whenever if any single value contains null at that time this function always returns null (Thanks to user @sanghavi7)

Best Answer

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Mysql – Should I use the datetime or timestamp data type in MySQL

Mysql – How to get the max of two values in MySQL

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