CUBRID学习笔记 27 数据类型四

范围比较

数字和字符串比较

字符串被转为double

SELECT i FROM t WHERE i <= all {'11','12'};

            i

=============

            1

            2

            3

            4

字符串和日期时间比较

字符串转为日期或时间

SELECT s FROM t2;

          s

======================

      '01/01/2000'

      '01/01/1999'

      '01/01/1998'

SELECT s FROM t2 WHERE s <= ALL {date'02/02/1998',date'01/01/2000'};

          s

======================

       '01/01/1998'

报错了

计算比较

Date/Time Type Operand

如果日期是间操作是-操作. 返回的是毫秒

SELECT date'2002-01-01' - datetime'2001-02-02 12:00:00 am';

   date '2002-01-01'- datetime '2001-02-02 12:00:00 am'

=====================================================

                                          28771200000

同类型比较看优先级

Date/Time Type & String Type Operands

如果有+-操作的话 结果如下

           DATE: 返回天

TIME, TIMESTAMP:返回 秒

DATETIME:返回 毫秒

SELECT date'2002-01-01' + '10';

  date '2002-01-01'+'10'

======================

  01/11/2002

SELECT date'2002-01-01'-'2001-01-01';

  date '2002-01-01'-'2001-01-01'

================================

                    31536000000

-- 下面的操作是不可以的

SELECT date'2002-01-01'-'10';

 In line 1, column 13,

 ERROR: 10不是日期类型.    

Numeric Type & String Type Operands

SELECT 4 + '5.2';

                4+'5.2'

==========================

  9.199999999999999e+00

SELECT '2002-01-01'+1;

   ERROR: 不能把'2002-01-01'转为double类型

SELECT DATE'2002-01-01'+1;

  date '2002-01-01'+1

=====================

  01/02/2002

String Type Operand

字符串的乘除操作返回double类型

SELECT '3'*'2';

                     '3'*'2'

============================

       6.000000000000000e+00

   字符串的加操作为连接操作.  ( 具体跟对加号的意义的配置有关 plus_as_concat 在 cubrid.conf中 )

• SELECT '1'+'1';
•  
•                '1'+'1'
• ======================
•                   '11'
• 如果plus_as_concat  没设置则
•  
•                    '1'+'1'
• ==========================
•      2.000000000000000e+00

An error will be returned if it cannot be converted to the corresponding type.