使用函式處理資料

*/substr();

substr();

substring();

substring(); --擷取字元

select substring(prod_name,2,6) from products ;

select prod_name from products;

select convert(varchar,prod_price) from products;

select * from products;

convert(); --轉換資料型別轉換

convert();

now();

select getdate() -- 獲取當前日期時間

select * from products where getdate()=getdate();

upper() -- 將字串轉換為大寫

select upper(products.prod_name) from products;

select left(products.prod_name,2) from products

select right(products.prod_name,3) from products;

lower()

select lower(prod_name) from products; --轉換字串為小寫 lower()

select upper(prod_name) from products; --轉換字串為大寫 upper()

select datalength(prod_name) from products; -- datalength() datalength() 返回的是總資料長度並不是當前列的資料長度

select len(prod_name) from products; -- len() len() 返回引數值的資料長度。當前列的資料長度 len 和 datalength 兩種函式 length不屬於函式

select ltrim(prod_name) from products; --去除字串左邊的空格 ltrim() 開頭l是 left(左 l) l的首字母

select rtrim(prod_name) from products; --去除字串右邊的空格 rtrim() 開頭r是 right(右 r)r的首字母

select soundex(prod_name) from products; -- 探測法：返回由四個字元組成的** 第乙個**是字串的首字母，數字為0 。剩餘字元安裝soundex函式的規則返回對應數值。

select cust_name,cust_contact from customers where soundex(cust_contact)=soundex('miqwael green');

select order_num from orders where datepart(yy,order_date)=2012 ;

select order_num from orders where order_date between ('2012-01-01') and ('2012-12-31'); --加上單引號可以查詢出想要的資料

select order_num from orders where order_date between (2012-01-01) and (2012-12-31); --不加單引號查詢不出想要的資料

select order_num from orders where order_date between convert(int,2012-01-01) and convert(int,2012-12-31); -- 查不到資料

select order_num from orders where order_date between convert(varchar,'2012-01-01') and convert(varchar,'2012-12-31'); --查得到資料

select prod_name from products;

select abs(prod_price) from products; --返回數值的絕對值

select cos(prod_price) from products; --

select exp(prod_price) from products;

select pi(); --返回圓周率

select sin(prod_price) from products;

select sqrt(prod_price) from products;

select tan(prod_price) from products;