Article Introduction：How to use the LEFTJOIN function in MySQL to get all the records of the left table. In MySQL, we can use the LEFTJOIN function to easily get all the records of the left table. LEFTJOIN is a join query method that returns all records in the left table and matches the corresponding records in the right table. The syntax of LEFTJOIN is as follows: SELECT column name FROM left table LEFTJOIN right table ON left table. column name = right table. column name;

2023-07-25 comment 0  2243

Article Introduction：Preface When we write SQL statements, we cannot avoid using connection keywords, such as inner connections and outer connections. There are many types. I will post here a picture I found elsewhere: I think this picture is very detailed. It shows the common link types in SQL statements. Take leftjoin in this article as an example. It is available online. As defined: the LEFTJOIN keyword will return all rows from the left table, even if there are no matching rows in the right table. In fact, literally speaking, leftjoin is relatively easy to understand, but there are still some problems during use. For example, if the condition is after on and after where, their results are completely different. Let's go from shallow to deep

2023-06-02 comment 0  1743

Article Introduction：Small Swoole Db 2.3 introduce left joins : $selector = (new TableSelector('user')) ->leftJoin('post', 'messageOwner', 'message') ; $selector->where() ->firstCondition(new Condition( new ConditionElement(ConditionElementTyp

2024-08-16 comment 0  1106

Article Introduction：To illustrate the production of MySQL views using LEFTJOIN, we use the following data from the "Customers" and "Resreve" tables -mysql>Select*fromcustomers;+-------------+---- ------+|Customer_Id|Name |+-------------+----------+|1 |Rahul &am

2023-09-02 comment 0  1426