How to delete a column from a table in MySQL

问题:

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?

回答1:

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.

回答2:

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;

回答3:

To delete a single column from a table you can use this:

ALTER TABLE table_name DROP COLUMN Column_name;

To delete multiple columns, do this:

ALTER TABLE table_name DROP COLUMN Column_name, DROP COLUMN Column_name;

回答4:

To delete columns from table.

ALTER TABLE tbl_Country DROP COLUMN IsDeleted1, DROP COLUMN IsDeleted2;

Or without word 'COLUMN'

ALTER TABLE tbl_Country DROP IsDeleted1, DROP IsDeleted2;

回答5:

To delete column use this,

ALTER TABLE `tbl_Country` DROP `your_col`

回答6:

You can use

alter table <tblname> drop column <colname>

回答7:

ALTER TABLE `tablename` DROP `columnname`;

Or,

ALTER TABLE `tablename` DROP COLUMN `columnname`;

回答8:

Use ALTER:

ALTER TABLE `tbl_Country` DROP COLUMN `column_name`;

回答9:

ALTER TABLE tbl_Country DROP columnName;

回答10:

ALTER TABLE `tbl_Country` DROP `IsDeleted`;

回答11:

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;

回答12:

When we perform an operation like deleting a column from the table it changes the structure of your table. For performing such kind of operation we need to use Data Definition Language (DDL) statements. In this case we have to use ALTER statement.

ALTER - alters the structure of the database

The query would be -

alter table tbl_Country drop column IsDeleted;