ORACLE 与 PostgreSQL 差别整理
<div class="blogstory">目前正在做一个项目得数据库迁移(oracle->postgresql),查找了一些资料将2者得差异整理如下:
ORACLE 与 PostgreSQL差别NO问题点OraclePostgreSQL1DUALSELECT 1+1 FROM DUALSELECT 1+1
或者
CREATE VIEW dual AS
SELECT 'X'::VARCHAR(1) AS DUMMY
再 SELECT 1+1 FROM DUAL
2NEXTVALSELECT A_TABLE_SEQUENCE.NEXTVAL
FROM DUALSELECT NEXTVAL('A_TABLE_SEQUENCE')
FROM DUAL
3ROWNUM①SELECT *
FROM AGE_TYPE
WHERE ROWNUM<=5①SELECT *
FROM AGE_TYPE
LIMIT 5 OFFSET 0
②SELECT *
FROM AGE_TYPE
WHERE CODE IS NOT NULL
AND ROWNUM<=5
ORDER BY CODE DESC②SELECT *
FROM
AGE_TYPE
WHERE CODE IS NOT NULL
ORDER BY CODE DESC
LIMIT 5 OFFSET 0
4(+)①SELECT *
FROM A_TABLE A , B_TABLE B
WHERE A.ID(+)=B.ID①SELECT *
FROM A_TABLE A
RIGHT OUTER JOIN
B_TABLE B
ON A.ID=B.ID
②SELECT *
FROM A_TABLE A , B_TABLE B
WHERE A.ID(+)=B.ID
AND A.COL1='COL1_VALUE'②SELECT *
FROM A_TABLE A
RIGHT OUTER JOIN B_TABLE B
ON A.ID=B.ID AND A.COL1='COL1_VALUE'
③SELECT *
FROM A_TABLE A, B_TABLE B,C_TABLE C,D_TABLE D
WHERE
A.ID=B.ID(+) AND
A.ID=C.ID(+) AND
A.COL1=D.COL1③SELECT *
FROM (A_TABLE A
LEFT OUTER JOIN B_TABLE B
ON A.ID=B.ID)
LEFT OUTER JOIN C_TABLE C
ON A.ID=C.ID,D_TABLE D
WHERE A.COL1=D.COL1
④!!!
SELECT *
FROM A_TABLE A
WHERE A.COL1(+)=0 AND
A.COL2(+) ='A_VALUE2'④!!!
SELECT *
FROM A_TABLE A
WHERE A.COL1=0 AND
A.COL2='A_VALUE2'
WHERE (A.COL1=0 OR A.COL1 IS NULL) AND
(A.COL2='A_VALUE2' OR A.COL2 IS NULL)
5ASSELECT A.COL1 A_COL1,
A.COL2 A_COL2
FROM A_TABLE ASELECT A.COL1 AS A_COL1,
A.COL2 AS A_COL2
FROM A_TABLE A
6NVLSELECT NVL(SUM(VALUE11),0) FS_VALUE1,
NVL(SUM(VALUE21),0) FS_VALUE2
FROM FIELD_SUM SELECT COALESCE(SUM(VALUE11),0) AS FS_VALUE1,
COALESCE(SUM(VALUE21),0) AS FS_VALUE2
FROM FIELD_SUM
7TO_
NUMBERSELECT COL1
FROM A_TABLE
ORDER BY TO_NUMBER(COL1)SELECT COL1
FROM A_TABLE
ORDER BY TO_NUMBER(COL1,999999)
[注：'999999' ---- 6位数为COL1字段的长度]
8DECODESELECT DECODE(ENDFLAG,'1','A','B') ENDFLAG
FROM TESTSELECT
(CASE ENDFLAG
WHEN '1' THEN 'A'
ELSE 'B' END) AS ENDFLAG
FROM TEST
9时间
问题UPDATE A_TABLE
SET ENTREDATE=SYSDATEUPDATE A_TABLE
SET ENTREDATE=TO_TIMESTAMP(CURRENT_TIMESTAMP,'YYYY-MM-DD HH24:MI:SS')
或者
UPDATE A_TABLE
SET ENTREDATE=CURRENT_TIMESTAMP
SELECT TO_DATE('20010203','YYYY-MM-DD') AS DAY
FROM DUALSELECT TO_DATE('20010203','YYYYMMDD') AS DAY
FROM DUAL
SELECT TO_DATE('20010203','YYYY-MM-DD') AS DAY
FROM DUAL
SELECT TO_DATE(SYSDATE,'YYYY-MM-DD') AS DAY
FROM DUALSELECT TO_DATE(CURRENT_DATE,'YYYY-MM-DD') AS DAY
FROM DUAL
SELECT TO_DATE(SYSDATE,'YYYY/MM/DD') AS DAY
FROM DUALSELECT TO_DATE(CURRENT_DATE,'YYYY/MM/DD') AS DAY
FROM DUAL
10||SELECT NULL||'-'||NULL AS VALUES1
FROM DUAL
SELECT COALESCE(NULL,'')||'-'||COALESCE(NULL,'') AS VALUES1
FROM DUAL
SELECT NULL||'-' ||NULL AS VALUES1
FROM DUAL
11aggregateSELECT ROUND(AVG(SUM(BASICCNT1))) BASICCNT
FROM ACCESS_INFO_SUM1_V
WHERE YEARCODE BETWEEN '200305' AND '200505'
GROUP BY SCCODESELECT ROUND(AVG(AIV.BASICCNT)) AS BASICCNT
FROM
(SELECT SUM(BASICCNT1) AS BASICCNT
FROM ACCESS_INFO_SUM1_V
WHERE YEARCODE BETWEEN '200305' AND '200505'
GROUP BY sccode
) AIV
12「"」①SELECT LENGTH('') AS VALUE1 FROM DUAL
VALUE1=NULL①SELECT LENGTH('') AS VALUE1 FROM DUAL
VALUE1=0
②SELECT TO_DATE('','YYYYMMDD') AS VALUE2
FROM DUAL
VALUE2=NULL②SELECT TO_DATE('','YYYYMMDD') AS VALUE2
FROM DUAL
VALUE2=0001-01-01 BC
③SELECT TO_NUMBER('',1) AS VALUE3 FROM DUAL
VALUE3=NULL③SELECT TO_NUMBER('',1) AS VALUE3 FROM DUAL
不能执行
④INSERT INTO TEST(VALUE4)VALUES('')
VALUE4=NULL (注：VALUE3字段为数值类型)④INSERT INTO TEST(VALUE4)VALUES('')
VALUE4=0
(注：VALUE4字段为数值类型)
⑤INSERT INTO TEST(VALUE5)VALUES('')
VALUE5=NULL (注：VALUE5字段为字符类型)⑤INSERT INTO TEST(VALUE5)VALUES('')
VALUE5=''
(注：VALUE5字段为字符类型,结果为长度为零的字符串)
⑥INSERT INTO TEST(VALUE6)VALUES(TO_DATE('','YYYYMMDD'))
VALUE6=NULL (注：VALUE6字段为时间类型)⑥INSERT INTO TEST(VALUE6)VALUES(TO_DATE('','YYYYMMDD'))
VALUE6=0001-01-01 BC
(注：VALUE7字段为时间类型)
13CEILSELECT CEIL(SYSDATE - TO_DATE('20051027 14:56:10','YYYYMMDD HH24:MI:SS')) AS DAYS
FROM DUALSELECT
EXTRACT(DAYFROM (TO_TIMESTAMP(CURRENT_TIMESTAMP,'YYYY-MM-DD-HH24-MI-SS')-TO_TIMESTAMP('2005-10-27 14:56:10','YYYY-MM-DD-HH24-MI-SS') ))+1 ASDAYS
FROM DUAL
14NULLIF无NULLIF函数SELECT NULLIF(VALUE1,VALUE2) AS COL1 FROM DUAL
[注]当VALUE1=VALUE2时，COL1=NULL
15CONCATCONCAT(CHAR,CHAR)创建函数来解决
CREATE FUNCTION CONCAT(CHAR,CHAR)
RETURNS CHAR AS
'SELECT $1 || $2' LANGUAGE 'sql';
16ADD_
MONTHSadd_months(date, int)创建函数来解决
CREATE FUNCTION add_months(date, int)
RETURNS date AS
'SELECT ($1 + ( $2::text || ''months'')::interval)::date;'
LANGUAGE 'sql'
17LAST
_DAYLAST_DAY(DATE)创建函数来解决
CREATE FUNCTION LAST_DAY(DATE)
RETURNS DATE AS
'SELECT date(substr(text($1 +
interval(''1 month'')),1,7)||''-01'')-1'
LANGUAGE 'sql';
18MONTHS
_BETWEENMONTH_BETWEEN(DATA,DATA)创建函数来解决
CREATE FUNCTION MONTH_BETWEEN(DATA,DATA)
RETURNS NUMERIC AS
'SELECT to_number((date($1)-
date($2)),''999999999'')/31'
LANGUAGE 'sql';
19GRE~
ATESTGREATEST (LEAST)创建函数来解决
CREATE OR REPLACE FUNCTION
GREATEST(TEXT[]) RETURNS TEXT AS '
DECLARE
ARRY ALIAS FOR $1;
GREATEST TEXT;
BEGIN
GREATEST := ARRY;
FOR I IN 1 .. ARRAY_UPPER(ARRY,1) LOOP
IF ARRY > GREATEST THEN
GREATEST := ARRY;
END IF;
END LOOP;
RETURN GREATEST;
END;
' LANGUAGE 'PLPGSQL';
SELECT GREATEST( ARRAY['HARRY','HARRIOT','HAROLD'])
AS "Greatest";
20BITANDBITAND(int,int)SELECT 値 & 値;
21子条件 在FROM子条件中字段须有列名，
处理方法用AS +别名
22MINUSMINUS以EXCEPT来替代
23BIN_
TO_
NUMSELECT BIN_TO_NUM(1,0,1,0) AS VALUE1 FROM DUALSELECT CAST(B'1010' AS INTEGER) AS VALUE1
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