SQL_DML_Add, delete and modify data in the table

DML: add, delete and modify data in the table

1. Add data:

• Syntax:
  * insert into table name (column name 1, column name 2, ... column name n) values ​​(value 1, value 2, ... value n);
• Note:
  1. The column name and value must correspond one to one.
  2. If the column name is not defined after the table name,
  insert into the table name values ​​(value 1, value 2, ... value n) is added to all columns by default ;
  3. In addition to numeric types, other types need to use quotation marks (single and double Can be caused

2. Delete data:

• Syntax:
  * delete from table name [where condition]

• Note:
  1. If no conditions are added, all records in the table will be deleted.
  2. If you want to delete all records

    * 1. delete from 表名; -- 不推荐使用。有多少条记录就会执行
    多少次删除操作
    * 2. TRUNCATE TABLE 表名; -- 推荐使用，效率更高 先删除表，
     然后再创建一张一样的表。
  

3. Modify the data:

• Syntax:
  * update table name set column name 1 = value 1, column name 2 = value 2,... [where condition];

• Note:
  1. If no conditions are added, all records in the table will be modified.