Some common operations of SQLServer and MySQL add fields, modify fields, and reset auto-increment IDs

Some common operations of SQLServer and MySQL

Summarize some common operations of SQLServer and MySQL, add fields, modify fields, reset auto-increment ID

add field

SQLServer

In SQLServer, we can use the ALTER TABLE command to add table fields. Specific steps are as follows:

1. Open SQL Server Management Studio.
2. In the Object Explorer, select the table to modify.
3. Right-click the table and choose Design.
4. In table design view, click in the bottommost blank column and enter the name of the field you want to add.
5. Select the type of data to add, set other properties such as default values, constraints, etc.
6. Click "Save" and that's it.

For example, to add a field named "age" to the table "users", the data type is int, you can follow the above steps.

MySQL

In MySQL, we can use the ALTER TABLE command to add table fields. Specific steps are as follows:

1. Open the MySQL command line client.
2. Select the database to modify:

USE [数据库名];

1. Run the following command:

ALTER TABLE [表名] ADD [字段名] [数据类型] [其他属性];

Among them, [table name] is the name of the table to be modified, [field name] is the name of the field to be added, [data type] is the type of data to be added, and [other attributes] can set default values, constraints, etc.

For example, to add a field named "age" to the table "users", with datatype int, you would run the following command:

ALTER TABLE users ADD age INT;

modify field

SQLServer

In SQLServer, we can use the ALTER TABLE command to modify table fields. Specific steps are as follows:

1. Open SQL Server Management Studio.
2. In the Object Explorer, select the table to modify.
3. Right-click the table and choose Design.
4. In table design view, find the field you want to modify, and make your changes.
5. Click "Save" and that's it.

For example, to modify the "age" field in the table "users" to "gender", you can follow the above steps.

MySQL

In MySQL, we can use the ALTER TABLE command to modify table fields. Specific steps are as follows:

1. Open the MySQL command line client.
2. Select the database to modify:

USE [数据库名];

1. Run the following command:

ALTER TABLE [表名] CHANGE [旧字段名] [新字段名] [数据类型] [其他属性];

Among them, [table name] is the table name to be modified, [old field name] is the field name to be modified, [new field name] is the modified field name, [data type] is the data type to be modified, [other Attributes] can set default values, constraints, etc.

For example, to change the field "age" in the table "users" to "gender" with a data type of varchar(10), you can run the following command:

ALTER TABLE users CHANGE age gender varchar(10);

Reset auto-increment ID

In SQLServer and MySQL, we often encounter the situation that the auto-increment ID will not return to the minimum value after deleting data. Here's how to set the auto-increment ID to start from a specified value:

SQLServer

In SQLServer, we can use the DBCC CHECKIDENT command to set the auto-increment ID to start from the specified value. Specific steps are as follows:

1. Open SQL Server Management Studio.
2. In the Object Explorer, select the table to modify.
3. Right-click the table and choose Design.
4. In Table Design view, select Auto-Increment Columns.
5. In the "Properties" window on the right, find the "Identity Specification" property and set it to "Yes".
6. Open a new query window and run the following command:

DBCC CHECKIDENT ('[表名]', RESEED, [起始值])

Among them, [table name] is the name of the table to be modified, and [start value] is the start value of the auto-increment column.

For example, to start the auto-increment column of table "users" from 100, you can run the following command:

DBCC CHECKIDENT ('users', RESEED, 100)

MySQL

In MySQL, we can use the ALTER TABLE command to set the auto-increment ID to start from the specified value. Specific steps are as follows:

1. Open the MySQL command line client.
2. Select the database to modify:

USE [数据库名];

1. Run the following command:

ALTER TABLE [表名] AUTO_INCREMENT = [起始值];

Among them, [table name] is the name of the table to be modified, and [start value] is the start value of the auto-increment column.

For example, to start the auto-increment column of table "users" from 100, you can run the following command: