CUBRID学习笔记 41 sql语法之select

cubrid的中sql查询语法

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SELECT [ ] <select_expressions>

[{TO | INTO} <variable_comma_list>]

[FROM <extended_table_specification_comma_list>]

[WHERE <search_condition>]

[GROUP BY {col_name | expr} [ASC | DESC], ...[WITH ROLLUP]]

[HAVING <search_condition> ]

[ORDER BY {col_name | expr} [ASC | DESC], ... [NULLS {FIRST | LAST}]

[LIMIT [offset,] row_count]

[USING INDEX { index_name [,index_name, ...] | NONE }]

[FOR UPDATE [OF <spec_name_comma_list>]]

<qualifier> ::= ALL | DISTINCT | DISTINCTROW | UNIQUE

<select_expressions> ::= * | <expression_comma_list> | *, <expression_comma_list>

<variable_comma_list> ::= [:] identifier, [:] identifier, ...

<extended_table_specification_comma_list> ::=
    <table_specification>   [
                                {, <table_specification> } ... |
                                <join_table_specification> ... |
                                <join_table_specification2> ...
                            ]

<table_specification> ::=

<single_table_spec> [] [WITH (<lock_hint>)] |

<metaclass_specification> [ ] |

|

TABLE ( )

::= [AS] [(<identifier_comma_list>)]

<single_table_spec> ::= [ONLY] <table_name> |

ALL <table_name> [ EXCEPT <table_name> ]

<metaclass_specification> ::= CLASS <class_name>

<join_table_specification> ::=

[INNER | {LEFT | RIGHT} [OUTER]] JOIN <table_specification> ON <search_condition>

<join_table_specification2> ::= CROSS JOIN <table_specification>

<lock_hint> ::= READ UNCOMMITTED

• 还是看例子吧

distinct 去重

SELECT DISTINCT host_nation

FROM olympic;

分页

SELECT host_year as col1, host_nation as col2

FROM olympic

ORDER BY col2 LIMIT 5;

SELECT CONCAT(host_nation, ', ', host_city) AS host_place

FROM olympic

ORDER BY host_place LIMIT 5;

还可以

SELECT 1+1 AS sum_value;

其实就类似子查询

SELECT SUM (n)

FROM (SELECT gold FROM participant WHERE nation_code = 'KOR'

UNION ALL

SELECT silver FROM participant WHERE nation_code = 'JPN') AS t(n);

换个姿势

SELECT nation_code, host_year, gold

FROM participant p

WHERE gold > (SELECT AVG(s)

FROM (SELECT silver + bronze

FROM participant

WHERE nation_code = p.nation_code

AND silver > 0

AND bronze > 0)

AS t(s));

where条件

WHERE <search_condition>

<search_condition> ::=
    <comparison_predicate>
    <between_predicate>
    <exists_predicate>
    <in_predicate>
    <null_predicate>
    <like_predicate>
    <quantified_predicate>
    <set_predicate>

  比较运算

  = <> != > < >= <=

  成立是1 不成立是0 

  any  some  all运算

  any 任一个条件符合 some 是一部分(文档暂缺)

  SELECT * FROM condition_tbl WHERE dept_name = ANY{'devel','sales'};

  all  条件全部符合

  SELECT * FROM condition_tbl WHERE salary > ALL{3000000, 4000000, NULL};

  SELECT * FROM condition_tbl WHERE (

(0.9 * salary) < ALL (SELECT salary FROM condition_tbl

WHERE dept_name = 'devel')

);

between 运算符

SELECT * FROM condition_tbl WHERE salary BETWEEN 3000000 AND 4000000;

SELECT * FROM condition_tbl WHERE (salary >= 3000000) AND (salary <= 4000000);

SELECT * FROM condition_tbl WHERE salary NOT BETWEEN 3000000 AND 4000000;

SELECT * FROM condition_tbl WHERE name BETWEEN 'A' AND 'E';

exists 运算符

SELECT 'raise' FROM db_root WHERE EXISTS(

SELECT * FROM condition_tbl WHERE salary < 2500000);

SELECT 'raise' FROM db_root WHERE NOT EXISTS(

SELECT * FROM condition_tbl WHERE salary < 2500000);

in 运算符

SELECT * FROM condition_tbl WHERE dept_name IN {'devel','sales'};

SELECT * FROM condition_tbl WHERE dept_name = ANY{'devel','sales'};

SELECT * FROM condition_tbl WHERE dept_name NOT IN {'devel','sales'};

isnull

SELECT * FROM condition_tbl WHERE salary IS NULL;

SELECT * FROM condition_tbl WHERE salary IS NOT NULL;

SELECT * FROM condition_tbl WHERE salary = NULL;

like 运算符

转义用

SELECT * FROM condition_tbl WHERE name LIKE '%s%';

SELECT * FROM condition_tbl WHERE UPPER(name) LIKE '_O%';

SELECT * FROM condition_tbl WHERE name LIKE '___';

REGEXP, RLIKE 运算符

这个例子用的少,转码比较

SELECT ('a' collate utf8_en_ci REGEXP BINARY 'A' collate utf8_en_ci);

0

SELECT ('a' collate utf8_en_cs REGEXP BINARY 'A' collate utf8_en_cs);

0

SELECT ('a' COLLATE iso88591_bin REGEXP 'A' COLLATE iso88591_bin);

1

SELECT ('a' COLLATE iso88591_bin REGEXP BINARY 'A' COLLATE iso88591_bin);

0

主要看这个

支持正则表达式喽

SELECT name FROM athlete where name REGEXP '^[1]';

下面更像是演示正则表达式

匹配特殊的字符

SELECT ('new\nline' REGEXP 'new

line');

SELECT ('cubrid dbms' REGEXP '^cub');

SELECT ('this is cubrid dbms' REGEXP 'dbms$');

SELECT ('cubrid dbms' REGEXP '^c.*$');

SELECT ('Aaaapricot' REGEXP '^A+pricot');

SELECT ('Apricot' REGEXP '^Aa?pricot');

SELECT ('Aapricot' REGEXP '^Aa?pricot');

('Aapricot' regexp '^Aa?pricot')

1 代表成立

SELECT ('Aaapricot' REGEXP '^Aa?pricot');

('Aaapricot' regexp '^Aa?pricot')

0

-- (cub)* : match zero or more instances of the sequence abc.

SELECT ('cubcub' REGEXP '^(cub)*$');

('cubcub' regexp '^(cub)*$')

1

-- [a-dX], [^a-dX] : matches any character that is (or is not, if ^ is used) either a, b, c, d or X.

SELECT ('aXbc' REGEXP '^[2]+');

('aXbc' regexp '^[3]+')

1

SELECT ('strike' REGEXP '^[a-dXYZ]+$');

('strike' regexp '^[a-dXYZ]+$')

1

case 运算符

SELECT a,

CASE WHEN a=1 THEN 'one'

WHEN a=2 THEN 'two'

ELSE 'other'

END

FROM case_tbl;

结果

a case when a=1 then 'one' when a=2 then 'two' else 'other' end

        1  'one'
        2  'two'
        3  'other'
     NULL  'other'

     SELECT a,
   CASE a WHEN 1 THEN 'one'
          WHEN 2 THEN 'two'
          ELSE 'other'
   END

FROM case_tbl;

SELECT a,

CASE WHEN a=1 THEN 1

WHEN a=2 THEN 1.2345

ELSE 1.234567890

END

FROM case_tbl;

SELECT a,

CASE WHEN a=1 THEN 'one'

WHEN a=2 THEN 'two'

ELSE 1.2345

END

FROM case_tbl; //报错,类型转换错误

COALESCE 函数

对null处理的函数

类似

CASE WHEN a IS NOT NULL

THEN a

ELSE b

END

当a的值为null的时候 返回10.0000

SELECT a, COALESCE(a, 10.0000) FROM case_tbl;

decode 函数

类似

CASE WHEN a = b THEN c

WHEN a = d THEN e

ELSE f

END

参数有三个,

第一个 可以是表达式要或者比较的值 如下例的a

第二个 结果 如下例的1 ,2

第三个 默认值 如other

a 列

1

2

3

NULL

执行

SELECT a, DECODE(a, 1, 'one', 2, 'two', 'other') FROM case_tbl;

结果

1 'one'

2 'two'

3 'other'

NULL 'other'

a为1 等于one a为2 等于two a为3和null ,没有符合条件的项,使用默认值other

SELECT a, DECODE(a, 1, 1, 2, 1.2345, 1.234567890) FROM case_tbl;

注意以下的结果,数字都是单精度的.隐式转换了. 以默认结果的类型为准.

1 1.000000000

2 1.234500000

3 1.234567890

NULL 1.234567890

下面的这个会失败,因为one不能转为 double

SELECT a, DECODE(a, 1, 'one', 2, 'two', 1.2345) FROM case_tbl;

GREATEST 函数

获取最大的值

SELECT gold, silver , bronze, GREATEST (gold, silver, bronze)

FROM participant

WHERE nation_code = 'KOR';

结果是三个参数列每行值中的的最大值

gold silver bronze greatest(gold, silver, bronze)

        9           12            9                              12
        8           10           10                              10
        7           15            5                              15
       12            5           12                              12
       12           10           11                              12

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if函数

三个参数,

第一个表达式返回真假

第二个表示真的时候返回的值

第三个表示假的时候返回的值

类似

CASE WHEN a IS TRUE THEN b

ELSE c

END

SELECT a, IF(a=1, 'one', 'other') FROM case_tbl;

IFNULL NVL函数

给null的列设默认值,注意返回的类型,取决于默认值的类型.ifnull和Nvl类似.但是Nvl支持集合类型.

类似

CASE WHEN a IS NULL THEN b

ELSE a

END

例如SELECT a, IFNULL(a, 'UNKNOWN') FROM case_tbl;

结果

1 '1'

2 '2'

3 '3'

NULL 'UNKNOWN'

ISNULL函数 返回整数 1或者0

LEAST函数

参数可以是多个表达式,返回最小的值, 参数是null则返回null

SELECT gold, silver , bronze, LEAST(gold, silver, bronze) FROM participant

WHERE nation_code = 'KOR';

结果

gold silver bronze least(gold, silver, bronze)

        9           12            9                            9
        8           10           10                            8
        7           15            5                            5
       12            5           12                            5
       12           10           11                           10

NULLIF 函数

相等返回null 否则原样返回

类似CASE

WHEN a = b THEN NULL

ELSE a

END

      SELECT a, NULLIF(a, 1) FROM case_tbl;
      结果 a是1的时候返回null
       a  nullif(a, 1)

        1          NULL
        2             2
        3             3
     NULL          NULL

NVL2(expr1, expr2, expr3) 函数

第一个表达式不等于null的是否返回第二个表达式,等于null返回第三个表达式

SELECT a, NVL2(a, a+1, 10.5678) FROM case_tbl;

     a  nvl2(a, a+1, 10.5678)

        1                      2
        2                      3
        3                      4
     NULL                     11

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1. a-d ↩︎

2. a-dXYZ ↩︎

3. a-dXYZ ↩︎