How to modify the content of a field in mysql

In mysql, you can use the UPDATE statement to modify the field content. This statement can update the contents of multiple fields. You only need to specify the field name and new value to be modified after the keyword SET. Between different fields Just separate them with commas ",", and the syntax is "UPDATE table name SET field name 1 = new value 1 [, field name 2 = new value 2...] [WHERE clause]". The "WHERE clause" is used to specify modification conditions. If omitted, the contents of all rows under the specified field will be modified. If not omitted, the contents of the specified row can be modified.

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

In mysql, you can use the UPDATE statement to modify field content.

MySQL UPDATE: Modify data (update data)

The UPDATE statement can modify and update data in one or more tables ( field content).

The UPDATE statement can update the contents of one or more fields in the table. You only need to specify the field name and new value to be modified after the keyword SET. Different fields are separated by commas "," That’s it.

Syntax:

UPDATE 表名 SET 字段名1=新值1 [,字段名2=新值2…] [WHERE 子句 ]

The syntax is as follows:

• Table name: used to specify the name of the table to be updated.

• SET clause : Used to specify the column name and column value to be modified in the table. Among them, each specified column value can be an expression or the default value corresponding to the column. If a default value is specified, the column value can be represented by the keyword DEFAULT.

• WHERE clause : Optional. Used to limit the rows in the table to be modified. If not specified, all rows in the table will be modified.

Note: When modifying multiple field values ​​in a row of data, each value in the SET clause can be separated by commas.

UPDATE statement example:

1. Modify the data in the table (omitting the WHERE clause)

In the tb_courses_new table, update the course_grade field value of all rows to 4.

mysql> UPDATE tb_courses_new SET course_grade=4;

Query OK, 3 rows affected (0.11 sec)
Rows matched: 4  Changed: 3  Warnings: 0

After updating, query the data to see if there is any change

mysql> SELECT * FROM tb_courses_new;

ok, you can see that all rows under the course_grade field are 4.

2. Modify the data in the table according to the conditions (do not omit the WHERE clause)

In the tb_courses table, update the record with course_id value 2 and change the course_grade field Change the value to 3.5 and change the course_name field value to "DB"

mysql> UPDATE tb_courses_new
    -> SET course_name='DB',course_grade=3.5
    -> WHERE course_id=2;

Query OK, 1 row affected (0.13 sec)
Rows matched: 1  Changed: 1  Warnings: 0

After updating, query the data to see if there is any change

mysql> SELECT * FROM tb_courses_new;

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