sql语言艺术（3）SQL的进攻式编程

update accountsset balance = balance-purchased_amountwhere balance>=purchased_amountand credit_limit>=purchased_amountand expiry_date>today()and customer_id =provided_idand card_num = provided_cardnum 

 

select c.customer_id, a.card_num, a.expiry_date,a.credit_limit,a.balancefrom customers c left outer join accounts a on a.customer_id = c.customer_id and a.card_num = provided_cardnumwhere c.customer_id = provided_id