一、sqlite中不能使用日期进行相减,执行结果无效
例如:SELECT count(*) as cnt FROM DayBanalces WHERE (date(ofDay)- date(‘2013-04-26 00:00:00’))=0 ×
正确: SELECT count(*) as cnt FROM DayBanalces WHERE (date(ofDay) = date(‘2013-04-26 00:00:00’))
二、sqlite中 0 与0.0的差别
首先先在数据库中创建1张表及插入少许数据
1 Create Table ZeroDemo 2 ( 3 id int identity(1,1),--在Sqlite中这句话的写法应该为:id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 4 num1 numeric(18,10), 5 num2 numeric(18,10), 6 numType int 7 ) 8 9 10 INSERT INTO ZeroDemo(num1,num2,numType) values(1,10,1) 11 INSERT INTO ZeroDemo(num1,num2,numType) values(2,20,1) 12 INSERT INTO ZeroDemo(num1,num2,numType) values(3,30,1) 13 INSERT INTO ZeroDemo(num1,num2,numType) values(4,40,1) 14 INSERT INTO ZeroDemo(num1,num2,numType) values(5,50,2) 15 INSERT INTO ZeroDemo(num1,num2,numType) values(1,1.19999,1)
通常SqlServer中我们的写法如下:
1 ---在SqlServer中如果某列的类型与所需要的列不一致,而又要统计合计sum值的时候,写法一般如下: 2 SELECT 3 4 SUM( 5 (CASE numType WHEN 1 THEN num1*num2 ELSE 0 end ) 6 ) as demosCoumns 7 8 FROM ZeroDemo
但是在sqlite中特别是操作Sum函数时候,一定要强制转成REAL类型, CAST(num1 as REAL)* CAST(num2 as REAL) ELSE CAST(0 AS REAL)
1 SELECT 2 3 SUM( 4 (CASE numType WHEN 1 THEN CAST(num1 as REAL)* CAST(num2 as REAL) ELSE CAST(0 AS REAL) end ) 5 ) as demosCoumns 6 7 FROM ZeroDemo
或者 0.0
SUM( (CASE numType WHEN 1 THEN num1*num2 ELSE 0.0 end ) ) as demosCoumns FROM ZeroDemo
以上sqlite在工具中执行的结果可能是一样的,但是如是你用.net调用System.Data.SQLite.dll的时候,如果你依然使用sqlserver的写法,那么可能出来的结果小数位数就会不见。具体的原因参见如下的文章: