[MySQL] basic use of explain and the function of each column

summary

Use EXPLAIN Keyword can simulate optimizer execution SQL Query statement , So they know MySQL How to deal with you SQL Of the statement . Analyze the performance bottleneck of your query statement or table structure .

adopt explain The results that can be obtained ：

• Read order of tables
• Operation type of data reading operation
• Which indexes can be used
• Which indexes can be actually used
• References between tables
• How many rows per table are queried by the optimizer

Basic grammar

EXPLAIN or DESCRIBE The syntax of the statement is as follows ：

EXPLAIN SELECT select_options 
 perhaps 
DESCRIBE SELECT select_options

Role of each column

EXPLAIN The functions of each column output by the statement are as follows ：

Detailed introduction ：