How to delete a column from a table in MySQL
MysqlDdlAlter TableMysql Problem Overview
Given the table created using:
CREATE TABLE tbl_Country
(
CountryId INT NOT NULL AUTO_INCREMENT,
IsDeleted bit,
PRIMARY KEY (CountryId)
)
How can I delete the column IsDeleted ?
Mysql Solutions
Solution 1 - Mysql
ALTER TABLE tbl_Country DROP COLUMN IsDeleted;
Here's a working example.
Note that the COLUMN keyword is optional, as MySQL will accept just DROP IsDeleted. Also, to drop multiple columns, you have to separate them by commas and include the DROP for each one.
ALTER TABLE tbl_Country
DROP COLUMN IsDeleted,
DROP COLUMN CountryName;
This allows you to DROP, ADD and ALTER multiple columns on the same table in the one statement. From the MySQL reference manual:
> You can issue multiple ADD, ALTER, DROP, and CHANGE clauses in a single ALTER TABLE statement, separated by commas. This is a MySQL extension to standard SQL, which permits only one of each clause per ALTER TABLE statement.
Solution 2 - Mysql
Use ALTER TABLE with DROP COLUMN to drop a column from a table, and CHANGE or MODIFY to change a column.
ALTER TABLE tbl_Country DROP COLUMN IsDeleted;
ALTER TABLE tbl_Country MODIFY IsDeleted tinyint(1) NOT NULL;
ALTER TABLE tbl_Country CHANGE IsDeleted IsDeleted tinyint(1) NOT NULL;
Solution 3 - Mysql
To delete a single column:
ALTER TABLE `table1` DROP `column1`;
To delete multiple columns:
ALTER TABLE `table1`
DROP `column1`,
DROP `column2`,
DROP `column3`;
Solution 4 - Mysql
You can use
alter table <tblname> drop column <colname>
Solution 5 - Mysql
ALTER TABLE `tablename` DROP `columnname`;
Or,
ALTER TABLE `tablename` DROP COLUMN `columnname`;
Solution 6 - Mysql
If you are running MySQL 5.6 onwards, you can make this operation online, allowing other sessions to read and write to your table while the operation is been performed:
ALTER TABLE tbl_Country DROP COLUMN IsDeleted, ALGORITHM=INPLACE, LOCK=NONE;
Solution 7 - Mysql
Use ALTER:
ALTER TABLE `tbl_Country` DROP COLUMN `column_name`;
Solution 8 - Mysql
ALTER TABLE tbl_Country DROP columnName;
Solution 9 - Mysql
It is worth mentioning that MySQL 8.0.23 and above supports Invisible Columns
CREATE TABLE tbl_Country(
CountryId INT NOT NULL AUTO_INCREMENT,
IsDeleted bit,
PRIMARY KEY (CountryId)
);
INSERT INTO tbl_Country VALUES (1, 1), (2,0);
ALTER TABLE tbl_Country ALTER COLUMN IsDeleted SET INVISIBLE;
SELECT * FROM tbl_Country;
CountryId
1
2
ALTER TABLE tbl_Country DROP COLUMN IsDeleted;
It may be useful in scenarios when there is need to "hide" a column for a time being before it could be safely dropped(like reworking corresponding application/reports etc.).