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mysql條件查詢if case用法

   where條件查詢

  代碼如下

  select * from news where DATE(adddate) between

  '2011-04-20' - INTERVAL 5 DAY and '2011-04-20' + INTERVAL 5 DAY

  select * from news where DATE(adddate) in ('2011-04-20','2011-04-15','2011-04-25')

  IF條件語句的使用

  mysql條件判斷語句if的使用:先判斷數據庫中是否存在是否存在指定值存在就修改不存在就添加。

  這裡我就用啦mysql存儲過程的if語句

  代碼如下

  DROP PROCEDURE IF EXISTS 過程名;

  CREATE PROCEDURE 過程名(

  IN trueName VARCHAR(100),

  IN phone VARCHAR(100),

  IN qqmsn VARCHAR(100),

  IN mail VARCHAR(100),

  IN mac VARCHAR(100),

  IN heartip VARCHAR(100)

  )

  NOT DETERMINISTIC

  SQL SECURITY DEFINER

  COMMENT ''

  BEGIN

  SELECT count(id) INTO @maccount from `表名` where `表名`.mac=mac; --是否存在此記錄

  if (@maccount>0) THEN

  update `表名` set `trueName`=trueName,`phone`=phone,`qqmsn`=qqmsn,`mail`=mail,`mac`=mac,

  `heart`=`heart`+1,`heartip`=heartip,`heartdatetime`=CURRENT_TIMESTAMP WHERE 表

  名.mac=mac;

  ELSE

  insert into `表名` (`trueName`,`phone`,`qqmsn`,`mail`,`mac`,`heartip`,`heartdatetime`)VALUES(trueName,phone,qqmsn,

mail,mac,heartip,CURRENT_TIMESTAMP);

  end IF;

  END

  case條件語句

  代碼如下

  select substr(t1.area_id, 1, 1) type,

  substr(t1.area_id, 2) id,

  case substr(t1.area_id, 1, 1)

  when 'c' then

  (select t2.country

  from countnumber.dbtable_countryid t2

  where t2.id = substr(t1.area_id, 2))

  else

  (select distinct t3.province

  from countnumber.dbtable_provinceid t3

  where t3.id = substr(t1.area_id, 2))

  end name

  from t_ad_area t1

  在第一個方案的返回結果中, value=compare-value。而第二個方案的返回結果是第一種情況的真實結果。如果沒有匹配的結果值,則返回結果為ELSE後的結果,如果沒有ELSE 部分,則返回值為 NULL。

  代碼如下

  mysql> SELECT CASE 1 WHEN 1 THEN 'one'

  -> WHEN 2 THEN 'two' ELSE 'more' END;

  -> 'one'

  mysql> SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END;

  -> 'true'

  mysql> SELECT CASE BINARY 'B'

  -> WHEN 'a' THEN 1 WHEN 'b' THEN 2 END;

  -> NULL

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