How to modify field type, length and add or delete columns in Mysql-Mysql Tutorial-php.cn

How to modify field type, length and add or delete columns in Mysql

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Release： 2023-06-02 19:04:02

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1. Modify the field length in mysql:

ALTER TABLE tb_article MODIFY COLUMN NAME VARCHAR(50);

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Here tb_article is the table name, NAME is the field name, and 50 is the modified length

2. Modify the field type in mysql:

ALTER TABLE tb_article MODIFY COLUMN NAME CHAR(50);

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After modification, the name field type changes from varchar to char

How to modify field type, length and add or delete columns in Mysql

##3. Add columns in mysql:

ALTER TABLE tb_article ADD COLUMN name1 VARCHAR(30);

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How to modify field type, length and add or delete columns in Mysql

4. Modify columns in mysql:

ALTER TABLE tb_article CHANGE name1 name2 VARCHAR(30);

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How to modify field type, length and add or delete columns in Mysql

name1 is the column name before modification, name2 is the modified column name Column name.

When modifying the column, you can also change the column type or length. Interested friends can try it themselves.

5. Delete columns in mysql

ALTER TABLE tb_article DROP COLUMN name2;

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How to modify field type, length and add or delete columns in Mysql

6. More examples of modifying field length in mysql

1. Modify one Field length

alter table table name modify column field name type;

For example: the test field in the demo table, the original length is 10 characters, the current length needs to be changed to 100 characters

alter table demo modify column test varchar(100);

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2. Modify the length of multiple fields

alter table table name modify column field name 1 type 1,

modify column field Name 2 Type 2,

modify column field name 3 Type 3;

For example: the test1, test2, and test3 fields in the demo table originally had a length of 10 characters, but the current length needs to be changed. into 100, 200, 300 characters

alter table demo modify column test1 varchar(100),

modify column test2 varchar(200),

modifycolumn test3 varchar(300);

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