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ä¾å¦ï¼å¨City-State-Zipåå建äºä¸åå¤åç´¢å¼ï¼é£ä¹ä»
对Stateåéå®æ¡ä»¶ä¸è½ä½¿ç¨è¿ä¸ªç´¢å¼ï¼å 为Stateä¸æ¯ç´¢å¼ç主åã
3ï¼ å¯¹ç´¢å¼ç主åæéå®æ¡ä»¶ï¼ä½æ¯å¨æ¡ä»¶è¡¨è¾¾å¼é使ç¨ä»¥ä¸è¡¨è¾¾å¼åä¼ä½¿ç´¢å¼å¤±æï¼é æå
¨è¡¨æ«æï¼
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Demo:
where upper(city)='TokYo' æ City || 'X' like 'TOKYO%',
select id from t where num/2=100 åºæ¹ä¸º: select id from t where num=100*2
select * from emp where to_char(hire_date,'yyyymmdd')='20080411' (ä¸ä½¿ç¨)
select * from emp where hire_date = to_char('20080411','yyyymmdd') (使ç¨)
ï¼2ï¼æ¥è¯¢å段is nullæ¶ç´¢å¼å¤±æï¼å¼èµ·å
¨è¡¨æ«æã
where City is null æ ,where City is not null,
解å³æ¹æ³ï¼SQLè¯æ³ä¸ä½¿ç¨NULLä¼æå¾å¤éº»ç¦ï¼æ好索å¼åé½æ¯NOT NULLçï¼å¯¹äºis nullï¼å¯ä»¥å»ºç«ç»åç´¢å¼ï¼nvl(å段,0),对表åç´¢å¼analyseåï¼is nullæ¥è¯¢æ¶å¯ä»¥éæ°å¯ç¨ç´¢å¼æ¥æ¾,ä½æ¯æçè¿ä¸æ¯å¼å¾è¯å®ï¼is not null æ¶æ°¸è¿ä¸ä¼ä½¿ç¨ç´¢å¼ãä¸è¬æ°æ®é大ç表ä¸è¦ç¨is nullæ¥è¯¢ã
select id from t where num is null
å¯ä»¥å¨numä¸è®¾ç½®é»è®¤å¼0ï¼ç¡®ä¿è¡¨ä¸numå没ænullå¼ï¼ç¶åè¿æ ·æ¥è¯¢ï¼
select id from t where num=0
(3)æ¥è¯¢æ¡ä»¶ä¸ä½¿ç¨äºä¸çäºæä½ç¬¦ï¼<>ã!=ï¼ä¼éå¶ç´¢å¼ãå¼èµ·å
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Where city!='TOKYO'.
解å³æ¹æ³ï¼éè¿æä¸çäºæä½ç¬¦æ¹æorï¼å¯ä»¥ä½¿ç¨ç´¢å¼ï¼é¿å
å
¨è¡¨æ«æãä¾å¦ï¼æcolumn<>âaaaâï¼æ¹æcolumn<âaaaâ or column>âaaaâï¼å°±å¯ä»¥ä½¿ç¨ç´¢å¼äºã
(4)对索å¼ç主åæéå®æ¡ä»¶ï¼ä½æ¯æ¡ä»¶ä½¿ç¨likeæä½ä»¥åå¼ä»¥â%âå¼å§æè
å¼æ¯ä¸ä¸ªèµå¼åéãä¾å¦ï¼
where City like '%YOK%'
where City like: City_bind_Variable xl_rao
select * from emp where name like '%A' (ä¸ä½¿ç¨ç´¢å¼)
select * from emp where name like 'A%' (使ç¨ç´¢å¼)
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ããâ%...âæ æ³ç´æ¥ä½¿ç¨ç´¢å¼ï¼ä½å¯ä»¥å©ç¨reverse + function indexçå½¢å¼ï¼ååælikeââ¦%âï¼å
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¨ç´¢å¼æ«æselect count(*) from emp5 where empno=7900; ç´¢å¼è·³è·å¼æ«æselect /*+ index(emp5 skip1)*/ count(*) from emp5 where empno=7900;åä¸ç§æ¯å
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