題目描述：
假如某系統包括客戶信息、賬戶餘額、資金明細表，其表結構如下：客戶信息表“clientinfo”（主鍵：custid)：
問題：
1) 找出未持有賬戶的客戶信息列表（輸出姓名、性別以及所屬分行）；
SELECT custname, custsex, branchid
FROM clientinfo
WHERE custid
NOT IN (SELECT cusid
FROM acctbalance);
2) 找出在2013年有交易發生的賬戶列表（輸出帳號、幣種、客戶姓名、性別）；
SELECT accountno, ccycode, custname, custsex
FROM clientinfo, acctbalance
WHERE accountno
IN (SELECT accountno
FROM funddetail
WHERE transdate
BETWEEN 20130101
AND 20131231);
3) 計算分行‘100000’所有賬戶的存款金額(按幣種輸出)；
SELECT SUM(currentbalance),ccycode
FROM ((SELECT c.branchid, a.currentbalance, a.ccycode
FROM clientinfo c
LEFT JOIN acctbalance a
ON c.custid = a.custid)
AS sheet)
WHERE sheet.branchid = 100000
GROUP BY ccycode;
4) 找出2013年未發生交易且賬戶餘額小於300的客戶列表（輸出帳號、幣種、客戶編號);
SELECT accountno, ccycode, custid
FROM acctbalance
WHERE currentbalance < 300
AND accountno
NOT IN (SELECT accountno
FROM funddetail
WHERE transdate
BETWEEN 20130101
AND 2013123);
5) 將賬戶餘額超過1000000且屬於分行‘300000’的客戶存款利率漲15%；
UPDATE acctbalance
SET interetrate = interestrate * 1.15
WHERE currentbalance > 100000
AND custid
IN (SELECT custid
FROM clientinfo
WHERE branchid = ‘300000’);