删除DataTable
Example :DROP TABLE TablenName
数据表取别名,在该 sql 语句中可以通过别名取字段
Example :SELECT u.email , p.productname FROM UserInfo u , ProductList p;
BETWEEN :取范围内的数据
SELECT username , dateline FROM UserInfo WHERE dateline BETWEEN Value1 and Value2;
从结果中取值:
SELECT username , dateline FROM UserInfo WHERE username IN (SELECT username FROM UserList);
SORT :先排序后取值
Example :SELECT username,dateline from UserInfo SORT BY dateline
Example :SELECT username,dateline from UserInfo SORT BY dateline DESC
Group by :一般用于取数量。取不重复值,没有重复项,Group by 后面的字段必须和 Select 后的项相同
Example :SELECT COUNT(*) email , producname from UserInfo GROUP BY email,productname;
DISTINCT:取不重复值,按照 DISTINCT 后所有列取唯一值
SELECT DISTINCT email FROM UserInfo;
限制小数位:转换为总长度为 18 小数位为 4 的数值型数字
SELECT CAST ((CAST(24 AS NUMERIC(18,4))/CAST(38 AS NUMERIC(18,4))) AS NUMERIC(18,4))
LEFT OUTER JOIN :结果中包含左边 UserInfo 所有 email ,右边 ProductList 没有就置空
SELECT email , pid FROM UserInfo U LEFT OUTER JOIN ProdcutList P ON U.email = P.email;
建立临时缓存表:
SELECT email , productname INTO #TempTable FROM UserInfo;