MySQL multi-Table Union query syntax example

MySQL multi-table joint query is a query method of MySQL database. The following describes the syntax of MySQL multi-table joint query for your reference.

MySQL multi-Table Union query syntax:

 
 

  
  
SELECT * FROM Insert table left join main table ON t1.lvid = t2.lv _ id
  
  
 
  
  
Select * from mytable, title where table name 1. name = table name 2. writer;
  
  
 
 
 

1. If mysql version is later than 4.0, use UNION for query. The example is as follows:

 
 

  
  
SELECT 'id', 'name', 'date', ''as 'type' FROM table_A WHERE condition statement ......
  
  
UNION
  
  
SELECT 'id', 'name', 'date', 'unfinished 'AS 'type' FROM table_ B WHERE condition statement ......
  
  
Order by 'id' LIMIT num;
  
  
 
 
 

2. If mysql version is earlier than 4.0, you need to create a temporary table in three steps. The example is as follows:

Step 1: create a temporary table tmp_table_name and insert related records in table_A

 
 

  
  
$ SQL = "CREATE TEMPORARY TABLE tmp_table_name SELECT 'id', 'name', 'date', 'complete the 'as 'type' FROM table_A WHERE Condition Statement ......";
  
  
Mysql_query ($ SQL) OR die ("query false !");
 
 

Step 2: obtain related records from table_ B and insert them to the temporary table tmp_table_name.

 
 

  
  
Mysql_query ("insert into tmp_table_name SELECT 'id', 'name', 'date2' AS 'date', 'unfinished 'as 'type' FROM table_ B WHERE Condition Statement ......") OR die ("query false !");
 
 

Step 3: retrieve records from the temporary table tmp_table_name

 
 

  
  
mysql_query(”SELECT * FROM tmp_table_name ORDER BY id DESC”) or die (”query false!”);  
 
 

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