标签：oralce sysdate 结果 重复 16px 需要 table reg 含义
| POSTGRESQL | |
|---|---|
| select * from (select rownum r,e.* from emp e where rownum <=5) t where r>0; | select * from emp limit 5 offset 0; |
| ORACLE | POSTGRESQL |
|---|---|
| select * from emp where rownum = 1; | select * from emp limit 1; |
| ORACLE | POSTGRESQL |
|---|---|
| select rownum,t.* from emp t; | select row_number() over(), t.* from emp t; |
| ORACLE | POSTGRESQL |
|---|---|
| SYSDATE | current_timestamp, current_date |
Oracle delete语句可以没有from，pg必须要有from
| ORACLE | POSTGRESQL |
|---|---|
| delete from emp where empno = xxx; delete emp where empno = xxx | delete from emp where empno = xxx |
Oracle支持类型自动转换，例如数字自动换换为字符串等；PG中需要显示转换，或者添加CAST
PostgreSQL在from关键字后的子查询必须要有别名，Oralce可以没有。
PG having语句必须在group by之后，oracle可以在group by之前
Oracle中使用start with … connect by…, PG中使用with recusive
| ORACLE | POSTGRESQL |
|---|---|
| select * from larearrelation where rearedgens = 1 and rearflag = 1 and rearlevel = ‘01’ connect by prior agentcode = rearagentcode start with rearagentcode = ‘10032226’; | with recursive rs as ( select * from larearrelation where rearagentcode = ‘10032226’ union all select a. *from larearrelation a, rs where a.rearagentcode = rs.agentcode ) select ** from rs where rearedgens = 1 and rearflag = ‘1’ and rearlevel = ‘01’ |
postgresql中update语句时，set的字段不能有别名
| ORACLE | POSTGRESQL |
|---|---|
| update emp t set t.name = ‘xxx’ where t.empno = 2 | update emp set name = ‘xxx’ where empno = 2 |
oracle日期相减自动转换为数字，结果为相差的天数。 pg日期相减为interval类型，得到相差天数需要进行类型转换
oracle的递归查询中level表示查询深度（或者递归层次），在PG中没有此含义的关键字，需要自行在with recursive实现
| ORACLE | POSTGRESQL |
|---|---|
| select max(level) from larearrelation where rearedgens = 1 and rearflag = 1 and rearlevel = ‘01’ connect by prior agentcode = rearagentcode start with rearagentcode = ‘10032226’; | with recursive rs as ( select larearrelation.*, 1 depth from larearrelation where rearagentcode = ‘10032226’ union all select a./**, rs.depth + 1 depth from larearrelation a, rs where a.rearagentcode = rs.agentcode ) select max(rs.depth) from rs where rearedgens = 1 and rearflag = ‘1’ and rearlevel = ‘01’ |
| ORACLE | POSTGRESQL |
|---|---|
| select seqname.nextval from dual; | select nextval(‘seqname’) |
Oralce外连接支持使用 (+)， PostgreSQL需使用left jion或者right join标准sql语法
oracle支持unique关键字去重复，pg中只能使用distinct
| ORACLE | POSTGRESQL |
|---|---|
| listagg | string_agg |
| ORACLE | POSTGRESQL |
|---|---|
| Minus | except |
null和’’在oracle中是一致的，最终都会存储为null，在PG中会进行区分
Oracle中 ! =，< >操作符中间允许有空格，PG中不可以
PG中无效的别名，可以尝试加as关键字，例如name
| ORACLE | POSTGRESQL |
|---|---|
| SELECT REGEXP_SUBSTR(‘17,20,23’,’,+’,1,1,’i’) FROM DUAL; | select (regexp_matches(‘17,20,23’, ‘,+’))[1] |
oracle字段名大写，PG字段名小写
标签：oralce sysdate 结果 重复 16px 需要 table reg 含义
原文地址：https://www.cnblogs.com/bors/p/PostgreSQL_Oracle.html
