Add multiple pieces of data to the data table
Method 1: Write multiple insert statements and separate them with English semicolons.
insert into students(name) value('小明');
insert into students(name) value('小张');
insert into students(name) value('小王');
Method 2: Insert multiple pieces of data through one insert statement. Use commas to separate multiple pieces of data. insert into table name value(...),(...),(...)
insert into students(name) value ('alex'),('zhangwu')
Data table modification operations
The keyword for the modification operation is update, and the keyword for conditional judgment is where syntax format:
update table name set field name 1 = value 1, field name 2 = value 2 where condition = xxx
update students set name ='heihei' where id =1
Notice:
Whenever you modify data, you must add conditional restrictions, otherwise the values of all records will be modified.
Delete data (understand)
The keyword of the delete operation is delete from, and the conditional judgment is where
delete from students where id = 2
Notice:
This method is physical deletion and is rarely used in work. Most of the work uses logical deletion.
Logical deletion is to define a field to identify that the current record has been deleted, such as adding a field, is_delete to identify whether it has been deleted, 1 means deleted, 0 means not deleted.
Other methods of deleting data: (Delete the table directly)
1truncate table table name, this method only deletes the data, not the table structure
2 drop table table name, this method deletes data and table structure
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