1.分页

Oracle： SELECT * FROM(SELECT A.*, ROWNUM RN FROM (select T.* from sj_receiptinfo t WHERE t.TAXNO LIKE CONCAT('%', CONCAT(?, '%')) order by t.id desc) A WHERE ROWNUM <= ?)WHERE RN > ?

mysql： select * from tableName where 条件 limit （当前页码*页面容量-1） , 页面容量pagesize

sqlServer： SELECT w2.n, w1.* FROM ARTICLE w1,( 　　SELECT TOP 1030 row_number() OVER (ORDER BY YEAR DESC, ID DESC) n, ID FROM ARTICLE) w2 WHERE w1.ID = w2.ID AND w2.n > 1000 ORDER BY w2.n ASC

postgresql：select * from xxx limit pagesize offset offsetNum ;

pagesize是固定的，即每页显示多少记录。offsetNum＝（当前页数－1）*pagesize

2.查询头5条记录

Oracle： SELECT * FROM PersonsWHERE ROWNUM <= 5

mysql:		SELECT * FROM Persons LIMIT 5

sqlServer:	SELECT TOP 2 * FROM Persons
postgresql：SELECT * FROM Persons LIMIT 5；跟mysql一样


3.模糊查询
Oracle：select T.* from sj_receiptinfo t WHERE t.TAXNO LIKE CONCAT('%', CONCAT(?, '%')) 
mysql：select T.* from sj_receiptinfo t WHERE t.TAXNO LIKE CONCAT('%', ？, '%') 

sqlServer：
select T.* from sj_receiptinfo t WHERE t.TAXNO LIKE ‘%%’
postgresql：select *，( T .类别代码 || '-' || T .发票号码 ) AS 号码 from account where username ~* 'baidu';
找出数据表account中所有用户名包含baidu且不区分大小写的用户的信息
4.判断null
Oracle：SELECT ProductName,UnitPrice*(UnitsInStock+NVL(UnitsOnOrder,0))FROM Products
mysql：SELECT ProductName,UnitPrice*(UnitsInStock+IFNULL(UnitsOnOrder,0))FROM Products
sqlServer：SELECT ProductName,UnitPrice*(UnitsInStock+ISNULL(UnitsOnOrder,0))FROM Products
postgresql：SELECT ProductName,UnitPrice*(UnitsInStock+COALESCE(UnitsOnOrder,0))FROM Products
5.插入数据
Oracle：insert into company(id,name,parentid,ccdm) values(COMPANY_SEQ.NEXTVAL,?,?,?)序列
mysql：insert into person(fullName,companyName) values(?,?) 因为ID是自动增长auto_increment
6.查询最大id
Oracle：SELECT NVL(MAX(ID),0)+1 FROM REPOT_BS