SQLServer、MySQL、Oracle语法差异小集锦

时间：2021-04-10 05:37:56

一、差异集锦

　　在建表的时候，只有自增的语法不同。

　　下面给出3种数据库通用的建表与初始化测试语句：

CREATE TABLE Country(

   Id int PRIMARY KEY,

   Name varchar(20)

);

CREATE TABLE Person (

  Id int PRIMARY KEY,

  CountryId int,

  Name varchar(20) NOT NULL UNIQUE,

  Sex int DEFAULT 0,

  CONSTRAINT FK_CID_PID FOREIGN KEY (CountryId) REFERENCES Country(Id)

);

　　插入测试数据：

INSERT INTO Country VALUES(1, '蜀国');

INSERT INTO Country VALUES(2, '魏国');

INSERT INTO Country VALUES(3, '吴国');

INSERT INTO Person VALUES(1,1,'刘备',1);

INSERT INTO Person VALUES(2,1,'关羽',1);

INSERT INTO Person VALUES(3,1,'张飞',1);

INSERT INTO Person VALUES(4,2,'曹操',1);

INSERT INTO Person VALUES(5,2,'郭嘉',1);

INSERT INTO Person VALUES(6,2,'典韦',1);

INSERT INTO Person VALUES(7,3,'孙权',1);

INSERT INTO Person VALUES(8,3,'周瑜',1);

INSERT INTO Person VALUES(9,3,'大乔',2);
  SQLServer MySQL Oracle
自增 identity(1,1)  AUTO_INCREMENT   SEQUENCE/触发器
自增行插入 INSERT INTO Person VALUES(NULL,1,'魏延',1) INSERT INTO Person VALUES(1,'魏延',1) INSERT INTO Person VALUES(SEQID.NEXTVAL,1,'魏延',1)
取前几条 SELECT TOP 5 * FROM Person  SELECT * FROM Person LIMIT 0,5 SELECT * FROM Person WHERE ROWNUM < 5
表别名 SELECT * FROM Person AS P INNER JOIN Country AS C ON P.CountryId = C.Id SELECT * FROM Person AS P INNER JOIN Country AS C ON P.CountryId = C.Id SELECT * FROM Person P INNER JOIN Country C ON P.CountryId = C.Id
字段名大小写  与SELECT相同 与SELECT相同 Oracle中，字段名都是大写的，即使SELECT语句中是小写，得到的结果也是大写。
获取当前时间&查询临时值  SELECT now() AS NOWDATE SELECT getdate() AS NOWDATE  SELECT sysdate AS NOWDATE FROM Dual--需加Dual虚表
       
       
       
       

　　

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