MySQL Development Tips (i)

I. Classification of SQL statements

• DDL Data Definition Language
• TPL Transaction Processing Language
• DCL Data Control Language
• DML Data Manipulation language

1. SELECT
2. INSERT
3. UPDATE
4. DELETE

Second, the importance of correct use of SQL

• Increase the efficiency of database processing and reduce the corresponding time of application
• Reduce database service load and increase server stability
• Reduce network traffic for inter-server communication

Third, development skills

• How to use the JOIN clause correctly

　　1.join Clauses---inside connections

SQL statement code:

2.join clause---left outer connection

　　　　SQL Statement Code:

　　　　

3.join clause---right outer connection

　　　　

　　　SQL Statement Code:

　　　　

4.join clauses---full connection

　　　　

　　　　Note: Full join is not supported in MySQL and you can use UNION all to query a SQL statement if you want to use the all connection

　　　　SQL Statement Code:

　　　　

5.join clauses---cross-linking

　　

SQL Statement Code:

　　　　

6. Updating tables with join

　　　　

7. Using join to refine subqueries

　　　　

optimized SQL statements:

　　　　

8. Using join to refine the aggregate subquery

　　　　　　　

The SQL statement is the most common date to find out about each person's blame:

　　　　The SQL statement is an optimized SQL statement:

　　　　

9. Group Selection

　　Group Query--row_number

　　　　NOTE: The following SQL statements are not supported in MySQL

　　　　

Group Query--group by

　　　　

　　　　

MySQL Development Tips (i)