计算VARCHAR字段中字符串的出现次数？

Question

我有这样一张桌子:

TITLE          |   DESCRIPTION
------------------------------------------------
test1          |   value blah blah value
test2          |   value test
test3          |   test test test
test4          |   valuevaluevaluevaluevalue

我试图弄清楚如何返回每个描述中字符串出现的次数.

所以,如果我想计算'value'出现的次数,sql语句将返回:

TITLE          |   DESCRIPTION                  |   COUNT
------------------------------------------------------------
test1          |   value blah blah value        |   2
test2          |   value test                   |   1
test3          |   test test test               |   0
test4          |   valuevaluevaluevaluevalue    |   5

有没有办法做到这一点？我根本不想使用php,只是mysql.

Answer 1

这应该做的伎俩:

SELECT 
    title,
    description,    
    ROUND (   
        (
            LENGTH(description)
            - LENGTH( REPLACE ( description, "value", "") ) 
        ) / LENGTH("value")        
    ) AS count    
FROM <table> 

Answer 2

试试这个:

 select TITLE,
        (length(DESCRIPTION )-length(replace(DESCRIPTION ,'value','')))/5 as COUNT 
  FROM <table> 

SQL小提琴演示

Answer 3

@yannis解决方案的更简单,更有效的变化:

SELECT 
    title,
    description,    
    CHAR_LENGTH(description) - CHAR_LENGTH( REPLACE ( description, 'value', '1234') ) 
        AS `count`    
FROM <table> 

不同之处在于我将"value"字符串替换为1-char较短的字符串(在本例中为"1234").这样您就不需要进行除法和舍入来获得整数值.

通用版本(适用于每个针头串):

SET @needle = 'value';
SELECT 
    description,    
    CHAR_LENGTH(description) - CHAR_LENGTH(REPLACE(description, @needle, SPACE(LENGTH(@needle)-1))) 
        AS `count`    
FROM <table> 

Answer 4

在SQL SERVER中,这就是答案

Declare @t table(TITLE VARCHAR(100), DESCRIPTION VARCHAR(100))

INSERT INTO @t SELECT 'test1', 'value blah blah value' 
INSERT INTO @t SELECT 'test2','value test' 
INSERT INTO @t SELECT 'test3','test test test' 
INSERT INTO @t SELECT 'test4','valuevaluevaluevaluevalue' 


SELECT TITLE,DESCRIPTION,Count = (LEN(DESCRIPTION) - LEN(REPLACE(DESCRIPTION, 'value', '')))/LEN('value') 

FROM @t

结果

TITLE   DESCRIPTION               Count
test1   value blah blah value        2
test2   value test                   1
test3   test test test               0
test4   valuevaluevaluevaluevalue    5

我没有安装MySQL,但是当REPLACE相同时,可以发现LEN的等效值是LENGTH.

所以MySql中的等价查询应该是

SELECT TITLE,DESCRIPTION, (LENGTH(DESCRIPTION) - LENGTH(REPLACE(DESCRIPTION, 'value', '')))/LENGTH('value') AS Count
FROM <yourTable>

如果它在MySql中也适用,请告诉我.

Answer 5

这是一个可以做到这一点的函数。

CREATE FUNCTION count_str(haystack TEXT, needle VARCHAR(32))
  RETURNS INTEGER DETERMINISTIC
  BEGIN
    RETURN ROUND((CHAR_LENGTH(haystack) - CHAR_LENGTH(REPLACE(haystack, needle, ""))) / CHAR_LENGTH(needle));
  END;