DML: deletions in the data table changes

1. Add data

　　(1) conventional additives

　　The INSERT  the INTO table name (column names, column names, column names) the VALUES (value, value, value);

　　

　　(2) simplified added

　　The INSERT  the INTO table name the VALUES (value, value, value);

　　

　　rule:

　　　　1) column names and values, and the number of data types must correspond.

　　　　2) simplified form of the addition, the need to assign all the columns, or can not be added. Not recommended for use.

　　　　3) In addition to numeric type, other types of data you need to add single quotes or double quotes .

 

2. Delete Data

　　(1) Delete accordance with the conditions

　　The DELETE  the FROM table name WHERE column name = condition;

　　(2) Empty Table

　　DELETE  the FROM table name; - delete efficiency is very low, there are few records on the implementation of several deletion

　　(3) reset table

　　TRUNCATE  TABLE table name; - after copying a table and then delete the table structure reconstruction, high-efficiency deleted

 

3. Modify the data

　　(1) basis for modifying

　　UPDATE table SET column name = value, a column name = value, a column name = value WHERE column name = condition;

　　(2) a plurality of modified

　　UPDATE table SET column name = value, column name = value, column name = value; - without conditions, all of the data in the table of target column will be modified unity