04. DML: Adding, deleting and modifying data in the table

04. DML: Adding, deleting and modifying data in the table

1. adding data:
   • grammar:
     • 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 should correspond one to one.
     2. If the column name is not defined after the table name, the default is to add values ​​to all columns
        insert into table name values ​​(value 1, value 2, ... value n);
     3. In addition to number types, other types need to be enclosed in quotation marks (single and double)
2. delete data:
   • grammar:
     • delete from table name [where condition]
   • note:
     1. If no conditions are added, all records in the table are deleted.
     2. If you want to delete all records
        1. delete from table name;-not recommended. How many delete operations will be performed as many records
        2. TRUNCATE TABLE table name;-recommended, it is more efficient to delete the table first, and then create the same table.
3. change the data:

   • grammar:

     • 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.