FETCH
目录
FETCH
NAMESYNOPSIS
DESCRIPTION æè¿°
PARAMETERS åæ°
OUTPUTS è¾åº
NOTES 注æ
EXAMPLES ä¾å
COMPATIBILITY å¼å®¹æ§
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NAME
FETCH - ç¨æ¸¸æ ä»æ¥è¯¢ä¸æåè¡
SYNOPSIS
FETCH [ direction { FROM | IN } ] cursorname
where direction can be empty or one of:
NEXT
PRIOR
FIRST
LAST
ABSOLUTE count
RELATIVE count
count
ALL
FORWARD
FORWARD count
FORWARD ALL
BACKWARD
BACKWARD count
BACKWARD ALL
DESCRIPTION æè¿°
FETCH 使ç¨æ¸¸æ æ£ç´¢è¡ã
ä¸ä¸ªæ¸¸æ æä¸ä¸ªç± FETCH 使ç¨çç¸å³èçä½ç½®ã 游æ å¾ä½ç½®å¯ä»¥å¨æ¥è¯¢ç»æç第ä¸è¡ä¹åï¼æèå¨ç»æä¸çä»»æè¡ï¼ æèå¨ç»æçæåä¸è¡ä¹åãå¨å建å®ä¹åï¼æ¸¸æ æ¯æ¾å¨ç¬¬ä¸è¡ä¹åçã å¨æåäºä¸äºè¡ä¹åï¼æ¸¸æ æ¾å¨æ£ç´¢å°çæåä¸è¡ä¸ãå¦æ FETCH æå®äºææå¯ç¨è¡ï¼é£ä¹å®å°±åå¨æåä¸è¡åé¢ï¼æèå¨ååæå»çæåµä¸æ¯åå¨ç¬¬ä¸è¡åé¢ã FETCH ALL æè FETCH BACKWARD ALL å°æ»æ¯æ游æ çä½ç½®æ¾å¨æåä¸è¡æèå¨ç¬¬ä¸è¡åé¢ã
NEXT, PRIOR, FIRST, LAST, ABSOLUTE, RELATIVE å½¢å¼å¨æ°å½å° 移å¨æ¸¸æ ä¹åæåä¸ä¸ªè¡ãå¦æ没ææ°æ®è¡äºï¼é£ä¹è¿åä¸ä¸ªç©ºçç»æï¼ é£ä¹æ¸¸æ å°±ä¼åå¨æ¥è¯¢ç»æçæåä¸è¡ä¹åæèå¨ç¬¬ä¸è¡ä¹åã
FORWARD å BACKWARD å½¢å¼å¨ååæèåå移å¨çè¿ç¨ä¸æåæå®çè¡æ°ï¼ ç¶åæ游æ å®ä½å¨æåè¿åçè¡ä¸ï¼æèæ¯ï¼å¦æ count 大äºå¯ç¨çè¡æ°ï¼å¨ææè¡ä¹åæä¹åãï¼
RELATIVE 0ï¼FORWARD 0ï¼å BACKWARD 0 é½è¦æ±å¨ä¸ç§»å¨æ¸¸æ çåæä¸æåå½åè¡ï¼ï¼ï¼ä¹å°±æ¯éæ°æåæè¿ååæåè¿çè¡ã é¤é游æå®ä½å¨ç¬¬ä¸è¡ä¹åæèæåä¸è¡ä¹åï¼è¿ä¸ªå¨ä½é½åºè¯¥æåï¼èå¨é£ä¸¤ç§æåµä¸ï¼ä¸è¿åä»»ä½è¡ã
PARAMETERS åæ°
direction
direction å®ä¹æåçæ¹ååæåçè¡æ°ãå®å¯ä»¥æ¯ä¸è¿°ä¹ä¸ï¼
|
NEXT |
æåä¸ä¸è¡ã direction çç¥æ¶è¿æ¯ç¼ºçå¼ã
|
PRIOR |
æååé¢ä¸è¡ã
|
FIRST |
æåæ¥è¯¢ç第ä¸è¡ï¼å ABSOLUTE 1 ç¸åï¼ã
|
LAST |
æåæ¥è¯¢çæåä¸è¡ï¼å ABSOLUTE -1 ç¸åï¼ã
ABSOLUTE count
æåæ¥è¯¢ä¸ç¬¬ count è¡ï¼ æèï¼å¦æ count < 0ï¼ ä»æ¥è¯¢ç»ææ«å°¾æå第abs(count)è¡ã å¦æcount è¶åºäºèå´ï¼é£ä¹å®ä½å¨ç¬¬ä¸è¡ä¹ååæåä¸è¡ä¹åçä½ç½®ï¼ ç¹å«æ¯ ABSOLUTE 0 å®ä½å¨ç¬¬ä¸è¡ä¹åã
RELATIVE count
æåéåç第 count è¡ï¼ æèï¼å¦æ count < 0 çæ¶åï¼ æååé¢ç第 abs(count) è¡ã å¦æææ°æ®çè¯ï¼RELATIVE 0 éæ°æåå½åè¡ã
|
count |
æåä¸é¢ç count è¡ ï¼å FORWARD count ä¸æ ·ï¼ã
|
ALL |
æåææå©ä½çè¡ï¼å FORWARD ALL ä¸æ ·ï¼ã
FORWARD
æåä¸é¢ä¸è¡ï¼å NEXTï¼ä¸æ ·ã
FORWARD count
æåä¸é¢ count è¡ã FORWARD 0 éæ°æåå½åè¡ã
FORWARD ALL
æåææå©ä½è¡ã
BACKWARD
æååé¢ä¸è¡ï¼å PRIOR ä¸æ ·ï¼ã
BACKWARD count
æååé¢ count è¡ï¼ååæ«æï¼ã BACKWARD 0 éæ°æåå½åè¡ã
BACKWARD ALL
æåææåé¢çè¡ï¼ååæ«æï¼ã
|
count |
count å¯è½æ¯ä¸ä¸ªæ符å·çæ´æ°å¸¸éï¼å³å®è¦æåçè¡æ°åæ¹åã å¯¹äº FORWARD å BACKWARD çæåµï¼å£°æä¸ä¸ªå¸¦è´å·ç count çæäºæ¹å FORWARD å BACKWARD çæ¹åã |
cursorname
ä¸ä¸ªæå¼ç游æ çå称ã
OUTPUTS è¾åº
æåå®ææ¶ï¼ä¸ä¸ª FETCH å½ä»¤è¿åä¸ä¸ªå½¢å¦ä¸é¢çæ è®°
FETCH count
è¿éç count æ¯æåçè¡æ°ï¼å¯è½æ¯é¶ï¼ã 请注æå¨ psql éï¼å½ä»¤æ ç- ¾å®éä¸ä¸ä¼æ¾ç¤ºï¼ å 为 psql ç¨æåçè¡æ°å代äºã
NOTES 注æ
å¦æä½ æ³ä½¿ç¨ FETCH NEXT ä¹å¤çä»»ä½ FETCH çåç§ï¼ æèæ¯å¸¦è´æ°è®¡æ°ç FETCH FORWARDãé£ä¹å®ä¹æ¸¸æ çæ¶ååºè¯¥å¸¦ç SCROLL é项ã 对äºç®åçæ¥è¯¢ï¼PostgreSQL ä¼å许é£äºæ²¡æ带 SCROLL é项å®ä¹ç游æ ä¹å¯ä»¥ååæåï¼ ä½æ¯æ们æ好ä¸è¦ä¾èµè¿ä¸ªè¡ä¸ºã å¦æ游æ å®ä¹äº NO SCROLLï¼é£ä¹ä¸å许ååæåã
ABSOLUTE æåä¸ä¼æ¯ç¨ç¸å¯¹ä½ç§»ç§»å¨å°éè¦çæ°æ®è¡æ´å¿«ï¼ å 为ä¸å±çå®ç°å¿é¡»éåææä¸é´çè¡ãè´æ°çç»å¯¹æåçè³æ´ç³ç³ï¼ æ¥è¯¢å¿é¡»ä¸ç´è¯»å°ç»å°¾æè½æ¾å°æåä¸è¡ï¼ç¶åä»é£éå¼å§ååéåã ä¸è¿ï¼åéå°æ¥è¯¢å¼å¤´ï¼å°±å FETCH ABSOLUTE 0ï¼å¾å¿«ã
å¨æ¸¸æ ä¸æ´æ°æ°æ®è¿ä¸è¢« PostgreSQL æ¯æã
DECLARE [declare(7)] è¯å¥ç¨äºå®ä¹ä¸ä¸ªæ¸¸æ ãä½¿ç¨ MOVE [move(7)] è¯- å¥æ¥æ¹å游æ ä½ç½®èä¸æ£ç´¢æ°æ®ã
EXAMPLES ä¾å
ä¸é¢çä¾åç¨ä¸ä¸ªæ¸¸æ è·¨è¿ä¸ä¸ªè¡¨ã
BEGIN WORK;
--
建ç«ä¸ä¸ªæ¸¸æ ï¼
DECLARE liahona SCROLL CURSOR FOR SELECT * FROM films;
--
æå头 5
è¡å°æ¸¸æ
liahona éï¼
FETCH FORWARD 5 FROM liahona;
code | title |
did | date_prod | kind | len
-------+-------------------------+-----+------------+----------+-------
BL101 | The Third Man | 101 | 1949-12-23 | Drama | 01:44
BL102 | The African Queen | 101 | 1951-08-11 | Romantic |
01:43
JL201 | Une Femme est une Femme | 102 | 1961-03-12 |
Romantic | 01:25
P_301 | Vertigo | 103 | 1958-11-14 | Action | 02:08
P_302 | Becket | 103 | 1964-02-03 | Drama | 02:28
--
æååé¢è¡ï¼
FETCH PRIOR FROM liahona;
code | title |
did | date_prod | kind | len
-------+---------+-----+------------+--------+-------
P_301 | Vertigo | 103 | 1958-11-14 | Action | 02:08
--
å³é游æ 并æ交äºå¡ï¼
CLOSE liahona;
COMMIT WORK;
COMPATIBILITY å¼å®¹æ§
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æ¶å FORWARD å BACKWARD ç FETCH å½¢å¼ ï¼åæ¬ FETCH count å FETCH ALL çå½¢å¼ï¼è¿ä¸ªæ¶å FORWARD æ¯éå«çï¼æ¯ PostgreSQL çæ©å±ã
SQL æ ååªå许游æ åé¢æ FROMï¼ ç¨ IN æ¯ä¸ç§æ©å±ã
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man
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