mysql的算术运算符和比较运算符

mysql 的算术部分

mysql> create table tmpl4(num int);
Query OK, 0 rows affected (0.14 sec)

mysql> insert into tmpl4 values(64);
Query OK, 1 row affected (0.08 sec)

mysql> select num,num+10,num-3+5,num+5-3,num+36.5 from tmpl4;
+------+--------+---------+---------+----------+
| num  | num+10 | num-3+5 | num+5-3 | num+36.5 |
+------+--------+---------+---------+----------+
|   64 |     74 |      66 |      66 |    100.5 |
+------+--------+---------+---------+----------+
1 row in set (0.00 sec)

mysql> select num,num*2,num/2,num/3,num%3 from tmpl4;
+------+-------+---------+---------+-------+
| num  | num*2 | num/2   | num/3   | num%3 |
+------+-------+---------+---------+-------+
|   64 |   128 | 32.0000 | 21.3333 |     1 |
+------+-------+---------+---------+-------+
1 row in set (0.00 sec)

mysql> select  num,num/0,num%0 from tmpl4;
+------+-------+-------+
| num  | num/0 | num%0 |
+------+-------+-------+
|   64 |  NULL |  NULL |
+------+-------+-------+
1 row in set (0.00 sec)

mysql>

mysql 的比较运算部分

---+----------+
1 row in set (0.00 sec)

mysql> select 1<=>0,'2'<=>2,2<=>2,'0.02'<=>0,'b'<=>'b',(1+3) <=> (2+1),NULL<=>NU
LL,1<=>NULL\G
*************************** 1. row ***************************
          1<=>0: 0
        '2'<=>2: 1
          2<=>2: 1
     '0.02'<=>0: 0
      'b'<=>'b': 1
(1+3) <=> (2+1): 0
    NULL<=>NULL: 1
       1<=>NULL: 0
1 row in set (0.00 sec)

mysql> <> or != 用于判断数字，字符串，表达式不相等的判断,如果不相等，返回值为1，
否则返回值为0.这两个运算符不能用于判断空值NULLmysql> Ctrl-C -- exit!

mysql> select 'good' <> 'god',1<>2,4!=4,5!=5,(1+3)!=(2+1),NULL <>NULL;
+-----------------+------+------+------+--------------+-------------+
| 'good' <> 'god' | 1<>2 | 4!=4 | 5!=5 | (1+3)!=(2+1) | NULL <>NULL |
+-----------------+------+------+------+--------------+-------------+
|               1 |    1 |    0 |    0 |            1 |        NULL |
+-----------------+------+------+------+--------------+-------------+
1 row in set (0.00 sec)

mysql> select 'good' <= 'god',1<=2,4<=4,5.5<5,(1+3)<=(2+1),NULL<=NULL;
+-----------------+------+------+-------+--------------+------------+
| 'good' <= 'god' | 1<=2 | 4<=4 | 5.5<5 | (1+3)<=(2+1) | NULL<=NULL |
+-----------------+------+------+-------+--------------+------------+
|               0 |    1 |    1 |     0 |            0 |       NULL |
+-----------------+------+------+-------+--------------+------------+
1 row in set (0.00 sec)

mysql> select 'good'<'god',1<2,4<4,5.5<5,(1+3)<(2+1),NULL
| 'good'<'god' | 1<2 | 4<4 | 5.5<5 | (1+3)<(2+1) | NULL
|            0 |   1 |   0 |     0 |           0 |      NULL |
+--------------+-----+-----+-------+-------------+-----------+
1 row in set (0.00 sec)

mysql> select 'good' >='god',1>=2,4>=4,5.5>5,(1+3)>=(2+1),NULL>=NULL;
+----------------+------+------+-------+--------------+------------+
| 'good' >='god' | 1>=2 | 4>=4 | 5.5>5 | (1+3)>=(2+1) | NULL>=NULL |
+----------------+------+------+-------+--------------+------------+
|              1 |    0 |    1 |     1 |            1 |       NULL |
+----------------+------+------+-------+--------------+------------+
1 row in set (0.00 sec)

mysql> select NULL is NULL,ISNULL(NULL),ISNULL(10),10 is NOT NULL;
+--------------+--------------+------------+----------------+
| NULL is NULL | ISNULL(NULL) | ISNULL(10) | 10 is NOT NULL |
+--------------+--------------+------------+----------------+
|            1 |            1 |          0 |              1 |
+--------------+--------------+------------+----------------+
1 row in set (0.00 sec)

mysql> select 4 between 4 and 6,4 between 4 and 6,12 between 9 and 10;
+-------------------+-------------------+---------------------+
| 4 between 4 and 6 | 4 between 4 and 6 | 12 between 9 and 10 |
+-------------------+-------------------+---------------------+
|                 1 |                 1 |                   0 |
+-------------------+-------------------+---------------------+
1 row in set (0.00 sec)

mysql> select 'x' between  'f' and 'g','b' between 'a' and 'c';
+--------------------------+-------------------------+
| 'x' between  'f' and 'g' | 'b' between 'a' and 'c' |
+--------------------------+-------------------------+
|                        0 |                       1 |
+--------------------------+-------------------------+
1 row in set (0.00 sec)

mysql> select least(2,0),least(20.0,3.0,100.5),least('a','c','b'),least(0,NULL);

+------------+-----------------------+--------------------+---------------+
| least(2,0) | least(20.0,3.0,100.5) | least('a','c','b') | least(0,NULL) |
+------------+-----------------------+--------------------+---------------+
|          0 |                   3.0 | a                  |          NULL |
+------------+-----------------------+--------------------+---------------+
1 row in set (0.00 sec)

mysql> select greatest(2,0),greatest(20.0,3.0,100.5),greatest('a','c','b'),great
est(10,NULL);
+---------------+--------------------------+-----------------------+------------
-------+
| greatest(2,0) | greatest(20.0,3.0,100.5) | greatest('a','c','b') | greatest(10
,NULL) |
+---------------+--------------------------+-----------------------+------------
-------+
|             2 |                    100.5 | c                     |
  NULL |
+---------------+--------------------------+-----------------------+------------
-------+
1 row in set (0.00 sec)

mysql> select greatest(2,0),greatest(20.0,3.0,100.5),greatest('a','c','b'),great
est(10,NULL)\G
*************************** 1. row ***************************
           greatest(2,0): 2
greatest(20.0,3.0,100.5): 100.5
   greatest('a','c','b'): c
       greatest(10,NULL): NULL
1 row in set (0.00 sec)

mysql> select 1 in(1,3,5,'thks'),'thks' in (1,3,5,'thks');
+--------------------+--------------------------+
| 1 in(1,3,5,'thks') | 'thks' in (1,3,5,'thks') |
+--------------------+--------------------------+
|                  1 |                        1 |
+--------------------+--------------------------+
1 row in set, 1 warning (0.01 sec)

mysql> select 2 not in (1,3,5,'thks'),'thks' not in(1,3,5,'thks');
+-------------------------+-----------------------------+
| 2 not in (1,3,5,'thks') | 'thks' not in(1,3,5,'thks') |
+-------------------------+-----------------------------+
|                       1 |                           0 |
+-------------------------+-----------------------------+
1 row in set, 2 warnings (0.00 sec)

mysql> select null in (1,3,5,'thks'),10 in (1,3,NULL,'thks');
+------------------------+-------------------------+
| null in (1,3,5,'thks') | 10 in (1,3,NULL,'thks') |
+------------------------+-------------------------+
|                   NULL |                    NULL |
+------------------------+-------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> select 'stud' like 'stud','stud' like 'stu_','stud' like '%d','stud' like
 't___','s' like NULL;
+--------------------+--------------------+------------------+------------------
--+---------------+
| 'stud' like 'stud' | 'stud' like 'stu_' | 'stud' like '%d' | 'stud' like 't___
' | 's' like NULL |
+--------------------+--------------------+------------------+------------------
--+---------------+
|                  1 |                  1 |                1 |
0 |          NULL |
+--------------------+--------------------+------------------+------------------
--+---------------+
1 row in set (0.00 sec)

mysql> select 'stud' like 'stud','stud' like 'stu_','stud' like '%d','stud' like
 't___','s' like NULL\G
*************************** 1. row ***************************
'stud' like 'stud': 1
'stud' like 'stu_': 1
  'stud' like '%d': 1
'stud' like 't___': 0
     's' like NULL: NULL
1 row in set (0.00 sec)

mysql> select 'ssky' regexp '^s','ssky' regexp 'y$','ssky' regexp '.sky','ssky'
regexp '[ab]';
+--------------------+--------------------+----------------------+--------------
--------+
| 'ssky' regexp '^s' | 'ssky' regexp 'y$' | 'ssky' regexp '.sky' | 'ssky' regexp
 '[ab]' |
+--------------------+--------------------+----------------------+--------------
--------+
|                  1 |                  1 |                    1 |
      0 |
+--------------------+--------------------+----------------------+--------------
--------+
1 row in set (0.01 sec)

mysql> select 'ssky' regexp '^s','ssky' regexp 'y$','ssky' regexp '.sky','ssky'
regexp '[ab]'\G
*************************** 1. row ***************************
  'ssky' regexp '^s': 1
  'ssky' regexp 'y$': 1
'ssky' regexp '.sky': 1
'ssky' regexp '[ab]': 0
1 row in set (0.00 sec)

mysql> select not 10,not(1-1),not-5,not NULL,not !1+1;
+--------+----------+-------+----------+----------+
| not 10 | not(1-1) | not-5 | not NULL | not !1+1 |
+--------+----------+-------+----------+----------+
|      0 |        1 |     0 |     NULL |        0 |
+--------+----------+-------+----------+----------+
1 row in set (0.00 sec)

mysql> select 1 and -1,1 and 0,1 and NULL,0 and NULL;
+----------+---------+------------+------------+
| 1 and -1 | 1 and 0 | 1 and NULL | 0 and NULL |
+----------+---------+------------+------------+
|        1 |       0 |       NULL |          0 |
+----------+---------+------------+------------+
1 row in set (0.00 sec)

mysql> select 1 && -1,1 && 0,1 && NULL,0 && NULL;
+---------+--------+-----------+-----------+
| 1 && -1 | 1 && 0 | 1 && NULL | 0 && NULL |
+---------+--------+-----------+-----------+
|       1 |      0 |      NULL |         0 |
+---------+--------+-----------+-----------+
1 row in set (0.00 sec)

mysql> select 1 or -1 or 0,1 or 2,1 or null,0 or null,null or null;
+--------------+--------+-----------+-----------+--------------+
| 1 or -1 or 0 | 1 or 2 | 1 or null | 0 or null | null or null |
+--------------+--------+-----------+-----------+--------------+
|            1 |      1 |         1 |      NULL |         NULL |
+--------------+--------+-----------+-----------+--------------+
1 row in set (0.01 sec)

mysql> select 1 || -1 || 0,1 || 2,1 || NULL,0 || NULL,NULL || NULL;
+--------------+--------+-----------+-----------+--------------+
| 1 || -1 || 0 | 1 || 2 | 1 || NULL | 0 || NULL | NULL || NULL |
+--------------+--------+-----------+-----------+--------------+
|            1 |      1 |         1 |      NULL |         NULL |
+--------------+--------+-----------+-----------+--------------+
1 row in set (0.00 sec)

mysql> select 1 xor 1,0 xor 0,1 xor 0,1 xor null,1 xor 1 xor 1;
+---------+---------+---------+------------+---------------+
| 1 xor 1 | 0 xor 0 | 1 xor 0 | 1 xor null | 1 xor 1 xor 1 |
+---------+---------+---------+------------+---------------+
|       0 |       0 |       1 |       NULL |             1 |
+---------+---------+---------+------------+---------------+
1 row in set (0.00 sec)

mysql> select 10 | 15;
+---------+
| 10 | 15 |
+---------+
|      15 |
+---------+
1 row in set (0.00 sec)

mysql> select 9|4|2;
+-------+
| 9|4|2 |
+-------+
|    15 |
+-------+
1 row in set (0.00 sec)

mysql> select 10 & 15;
+---------+
| 10 & 15 |
+---------+
|      10 |
+---------+
1 row in set (0.00 sec)

mysql> select 10^15;
+-------+
| 10^15 |
+-------+
|     5 |
+-------+
1 row in set (0.00 sec)

mysql> select 12<<2
    -> ;
+-------+
| 12<<2 |
+-------+
|    48 |
+-------+
1 row in set (0.00 sec)

mysql> select 12<<1;
+-------+
| 12<<1 |
+-------+
|    24 |
+-------+
1 row in set (0.00 sec)

mysql> select 1>>1;
+------+
| 1>>1 |
+------+
|    0 |
+------+
1 row in set (0.00 sec)

mysql> select 16 >> 2;
+---------+
| 16 >> 2 |
+---------+
|       4 |
+---------+
1 row in set (0.00 sec)

mysql> select 5 & ~1;
+--------+
| 5 & ~1 |
+--------+
|      4 |
+--------+
1 row in set (0.00 sec)

mysql>