ORDER BY排序子句:ASC(默认为升序),DESC(降序)
执行优先级:
3 SELECT
1 FROM
2 WHERE
4 ORDER BY
SQL@itkaifang> SELECT empno,ename,sal,deptno FROM emp WHERE deptno=20 ORDER BY empno; EMPNO ENAME SAL DEPTNO ---------- ---------- ---------- ---------- 7369 SMITH 800 20 7566 JONES 2975 20 7788 SCOTT 3000 20 7876 ADAMS 1100 20 7902 FORD 3000 20 SQL@itkaifang> SELECT empno,ename,sal,deptno FROM emp WHERE deptno=20 ORDER BY empno DESC ; EMPNO ENAME SAL DEPTNO ---------- ---------- ---------- ---------- 7902 FORD 3000 20 7876 ADAMS 1100 20 7788 SCOTT 3000 20 7566 JONES 2975 20 7369 SMITH 800 20 SQL@itkaifang> SELECT empno,ename,sal,comm,deptno FROM emp WHERE deptno=20 ORDER BY 3; EMPNO ENAME SAL COMM DEPTNO ---------- ---------- ---------- ---------- ---------- 7369 SMITH 800 20 7876 ADAMS 1100 20 7566 JONES 2975 20 7902 FORD 3000 20 7788 SCOTT 3000 20 SQL@itkaifang> SELECT empno,ename,sal,comm,deptno FROM emp WHERE sal>500 ORDER BY sal DES C,comm ASC; EMPNO ENAME SAL COMM DEPTNO ---------- ---------- ---------- ---------- ---------- 7839 KING 5000 10 7902 FORD 3000 20 7788 SCOTT 3000 20 7566 JONES 2975 20 7698 BLAKE 2850 30 7782 CLARK 2450 10 7499 ALLEN 1600 300 30 7844 TURNER 1500 0 30 7934 MILLER 1300 10 7521 WARD 1250 500 30 7654 MARTIN 1250 1400 30 7876 ADAMS 1100 20 7900 JAMES 950 30 7369 SMITH 800 20 14 rows selected. SQL@itkaifang> SELECT empno,ename,sal,comm FROM emp WHERE sal>500 ORDER BY 4; EMPNO ENAME SAL COMM ---------- ---------- ---------- ---------- 7844 TURNER 1500 0 7499 ALLEN 1600 300 7521 WARD 1250 500 7654 MARTIN 1250 1400 7788 SCOTT 3000 7839 KING 5000 7876 ADAMS 1100 7900 JAMES 950 7902 FORD 3000 7934 MILLER 1300 7698 BLAKE 2850 7566 JONES 2975 7369 SMITH 800 7782 CLARK 2450 14 rows selected. SQL@itkaifang>
ORDER BY
是唯一可使用别名的子句;
可用列的位置数指定排序;
列包含NULL值升序NULL在下方,反之则在上方。