sql查找重复数据
1.查找重复数据表的id以及重复数据的条数
select max(id) as nid,count(id) as 重复条数 from tableName
group by linkname Having Count(*) > 1
2.查找重复数据表的主键
select max(id) as nid from tableName
group by linkname Having Count(id) > 1
3.删除重复的数据
delete from tableName
where id in (
select max(id) as nid from tableName
group by linkname Having Count(id) > 1
)
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ORACLE PL/SQL与SQL SERVER T-SQL一些比较
字符串连接
Oracle用|| 符号作为连接符，而SQL Server的连接符是加号：+ 。
Oracle查询如下所示：Select ‘Name’ || ‘Last Name’ from tableName
SQL Server查询如下：Select ‘Name’ + ‘Last Name’
GUID
Oracle用SYS_GUID ......
import java.io.*;
import java.sql.*;
public class DBConn {
private String ADDRESS ;
private int PORT ;
private String DBNAME ;
private String USERNAME ;
private String PASSWORD ;
private Connection conn ;
private PreparedStatement pstmt ;
pri ......
SELECT ID,TITLE,
(SELECT TIMES from CLS_COURSE WHERE CLS_COURSE.ID=CLS_CLASS.COURSEID) AS TIMES,
(SELECT CASE WHEN EXISTS(SELECT * from CLS_ATDC WHERE CLS_ATDC.CLSID=CLS_CLASS.ID ) THEN (SELECT TOP 1 COURSETIME from CLS_ATDC WHERE CLS_ATDC.CLSID=CLS_CLASS.ID ORDER BY COURSETIME DESC) ELSE 0 ......
动态sql语句基本语法
1 :普通SQL语句可以用Exec执行
eg: Select * from tableName
Exec( ......
