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MYSQL DELETE COLUMN TO TABLE HOW TO
MYSQL DELETE COLUMN TO TABLE CODE

The algorithm_option allows you to specify a specific algorithm used for the index removal. Second, specify the name of the table to which the index belongs.First, specify the name of the index which you want to remove after the DROP INDEX keywords.To remove an existing index from a table, you use the DROP INDEX statement as follows: DROP INDEX index_name ON table_nameĬode language: SQL (Structured Query Language) ( sql )

MYSQL DELETE COLUMN TO TABLE HOW TO

In this tutorial, we have shown you how to use MySQL DROP COLUMN statement to remove one or more columns from a table.Summary: in this tutorial, you will learn how to use the MySQL DROP INDEX statement to remove existing indexes of a table. To avoid this error, you must remove the foreign key constraint before dropping the column.

MYSQL DELETE COLUMN TO TABLE CODE

Cannot drop index 'fk_cat': needed in a foreign key constraint Code language: JavaScript ( javascript ) MySQL issued an error message: Error Code: 1553. ALTER TABLE postsĭROP COLUMN category_id Code language: SQL (Structured Query Language) ( sql ) REFERENCES categories( id) Code language: SQL (Structured Query Language) ( sql )įourth, drop the category_id column from the posts table. Third, make the category_id column as a foreign key column of that references to the id column of the categories table. ALTER TABLE postsĪDD COLUMN category_id INT NOT NULL Code language: SQL (Structured Query Language) ( sql ) Second, add a column named category_id to the posts table. Consider the following example.įirst, create a table named categories: CREATE TABLE categories ( If you remove the column that is a foreign key, MySQL will issue an error. Then, view the table structure using the DESCRIBE statement: DESCRIBE posts Code language: SQL (Structured Query Language) ( sql )Īfter that, use the ALTER TABLE DROP COLUMN statement to drop the created_at and updated_at columns: ALTER TABLE postsĭROP COLUMN updated_at Code language: SQL (Structured Query Language) ( sql )įinally, use the DESCRIBE statement to verify the removal: DESCRIBE posts Code language: SQL (Structured Query Language) ( sql ) MySQL drop a column which is a foreign key example Next, use the ALTER TABLE DROP COLUMN statement to remove the excerpt column: ALTER TABLE postsĭROP COLUMN excerpt Code language: SQL (Structured Query Language) ( sql ) ) Code language: SQL (Structured Query Language) ( sql )

Dropping a column from a large table can impact the performance of the database during the removal time.įirst, create a table named posts for the demonstration.

The code from other applications that depends on the dropped column must be also changed, which takes time and efforts.

To fix it, you have to manually change the stored procedure’s code. When you remove the column, the stored procedure becomes invalid.

For example, you may have a stored procedure that refers to a column.

Removing a column from a table makes all database objects such as stored procedures, views, and triggers that referencing the dropped column invalid.

There are some important points you should remember before removing a column from a table: Code language: SQL (Structured Query Language) ( sql ) To remove multiple columns from a table using a single ALTER TABLE statement, you use the following syntax: ALTER TABLE table_name Note that the keyword COLUMN keyword in the DROP COLUMN clause is optional so you can use the shorter statement as follows: ALTER TABLE table_nameĭROP column_name Code language: SQL (Structured Query Language) ( sql )

Second, specify the name of the column that you want to drop in the DROP COLUMN clause.

First, specify the name of the table that contains the column which you want to drop after the ALTER TABLE keywords.In such cases, you use the following ALTER TABLE DROP COLUMN statement: ALTER TABLE table_nameĭROP COLUMN column_name Code language: SQL (Structured Query Language) ( sql ) In some situations, you want to remove one or more columns from a table. Introduction to MySQL DROP COLUMN statement Summary: in this tutorial, you will learn how to drop a column from a table using the MySQL DROP COLUMN statement.