SQLite Unions function
Translation results：
sqlite
Database; use; embedded relational database
unions
n. Union; Union plural noun); harmony; marriage
SQLite Unions functionsyntax
Function:SQLite's UNION clause/operator is used to combine the results of two or more SELECT statements without returning any duplicate rows.
In order to use UNION, the number of columns selected in each SELECT must be the same, the same number of column expressions, the same data type, and make sure they have the same order, but they do not have to have the same length .
Grammar: The basic syntax of UNION is as follows:
SELECT column1 [, column2 ]
FROM table1 [, table2 ]
[WHERE condition]
UNION
SELECT column1 [, column2 ]
FROM table1 [, table2 ]
[WHERE condition]
The conditions given here can be any expression as needed Mode.
SQLite Unions functionexample
COMPANY 表如下所示： sqlite> select * from COMPANY; ID NAME AGE ADDRESS SALARY ---------- -------------------- ---------- ---------- ---------- 1 Paul 32 California 20000.0 2 Allen 25 Texas 15000.0 3 Teddy 23 Norway 20000.0 4 Mark 25 Rich-Mond 65000.0 5 David 27 Texas 85000.0 6 Kim 22 South-Hall 45000.0 7 James 24 Houston 10000.0 （2）另一个表是 DEPARTMENT，如下所示： ID DEPT EMP_ID ---------- -------------------- ---------- 1 IT Billing 1 2 Engineering 2 3 Finance 7 4 Engineering 3 5 Finance 4 6 Engineering 5 7 Finance 6 现在，让我们使用 SELECT 语句及 UNION 子句来连接两个表，如下所示： sqlite> SELECT EMP_ID, NAME, DEPT FROM COMPANY INNER JOIN DEPARTMENT ON COMPANY.ID = DEPARTMENT.EMP_ID UNION SELECT EMP_ID, NAME, DEPT FROM COMPANY LEFT OUTER JOIN DEPARTMENT ON COMPANY.ID = DEPARTMENT.EMP_ID; 这将产生以下结果： EMP_ID NAME DEPT ---------- -------------------- ---------- 1 Paul IT Billing 2 Allen Engineerin 3 Teddy Engineerin 4 Mark Finance 5 David Engineerin 6 Kim Finance 7 James Finance