Shulou(Shulou.com)06/01 Report--

Below to bring you about the subquery of MySQL what is the usage and points for attention, I believe you must have read similar articles. What's the difference between what we bring to everyone? Let's take a look at the body. I'm sure you'll get something after reading the usage and precautions of the subquery of MySQL.

Sometimes a sql statement can not solve any problem, you need to nest sql statements to achieve the goal, but it will affect the efficiency of execution, here is a brief description of its usage and considerations. MySQL subqueries are queries that are nested within another query, such as SELECT,INSERT,UPDATE or DELETE. 1, MySQL subquery in the where clause =, >

(SELECT

AVG (amount)

FROM

Payments)

When a MySQL subquery in the FROM from clause uses a subquery in the MySQL clause, the result set returned from the subquery is used as a temporary table. This table is called a derived table or materialized subquery. SELECT MAX (items), MIN (items), FLOOR (AVG (items))

FROM

(SELECT

OrderNumber, COUNT (orderNumber) AS items

FROM

Orderdetails

GROUP BY orderNumber) AS lineitems

What are the usage and precautions of the above subquery about MySQL? do you think they want it? If you want to know more about it, you can continue to follow our industry information section.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.