WHERE clause syntax and examples - PolarDB

The WHERE clause filters rows from a query result. Only rows where the condition evaluates to TRUE are included in the output; rows where the condition evaluates to FALSE are discarded.

Syntax

WHERE condition

condition is any expression that evaluates to a BOOLEAN result.

Examples

Filter rows with a comparison

The following example joins the emp and dept tables and returns only rows where the deptno values match across both tables.

SELECT d.deptno, d.dname, e.empno, e.ename, e.mgr, e.hiredate
    FROM emp e, dept d
    WHERE d.deptno = e.deptno;

Output:

 deptno |   dname    | empno | ename  | mgr  |      hiredate
--------+------------+-------+--------+------+--------------------
     10 | ACCOUNTING |  7934 | MILLER | 7782 | 23-JAN-82 00:00:00
     10 | ACCOUNTING |  7782 | CLARK  | 7839 | 09-JUN-81 00:00:00
     10 | ACCOUNTING |  7839 | KING   |      | 17-NOV-81 00:00:00
     20 | RESEARCH   |  7788 | SCOTT  | 7566 | 19-APR-87 00:00:00
     20 | RESEARCH   |  7566 | JONES  | 7839 | 02-APR-81 00:00:00
     20 | RESEARCH   |  7369 | SMITH  | 7902 | 17-DEC-80 00:00:00
     20 | RESEARCH   |  7876 | ADAMS  | 7788 | 23-MAY-87 00:00:00
     20 | RESEARCH   |  7902 | FORD   | 7566 | 03-DEC-81 00:00:00
     30 | SALES      |  7521 | WARD   | 7698 | 22-FEB-81 00:00:00
     30 | SALES      |  7844 | TURNER | 7698 | 08-SEP-81 00:00:00
     30 | SALES      |  7499 | ALLEN  | 7698 | 20-FEB-81 00:00:00
     30 | SALES      |  7698 | BLAKE  | 7839 | 01-MAY-81 00:00:00
     30 | SALES      |  7654 | MARTIN | 7698 | 28-SEP-81 00:00:00
     30 | SALES      |  7900 | JAMES  | 7698 | 03-DEC-81 00:00:00
(14 rows)