问一个SQL语句的问题，关于检索条件里的括号

makeitbetter 2005-09-26 10:41:45

像下面一段的SQL语句，最后几个条件里的括号是什么意思啊，如果不加括号，结果会有什么差别？请指教。
SELECT ........
FROM .........
WHERE
b_t408.kaisha_code = i_kaisha_code
AND b_t408.keijonengetsu = i_batch_shori_ym
AND b_t408.sousai_haifu_kbn = '1'
AND b_t408.syukei_kbn = '0'
AND ( b_t408.keijoshiharai_kbn = '1'
AND b_t408.keiyakushubetsu = '2'
OR b_t408.keijoshiharai_kbn = '2'
AND b_t408.keiyakushubetsu = '1'
OR b_t408.keijoshiharai_kbn = '1'
AND b_t408.keiyakushubetsu = '4'
AND b_t408.choshu_kbn = '2')

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超叔csdn 2005-09-26

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AND 的优先级比OR 要高,所以先做AND 再做OR.
b_t408.kaisha_code = i_kaisha_code
AND b_t408.keijonengetsu = i_batch_shori_ym
AND b_t408.sousai_haifu_kbn = '1'
AND b_t408.syukei_kbn = '0'
AND ( b_t408.keijoshiharai_kbn = '1'
AND b_t408.keiyakushubetsu = '2'
OR b_t408.keijoshiharai_kbn = '2'
AND b_t408.keiyakushubetsu = '1'
OR b_t408.keijoshiharai_kbn = '1'
AND b_t408.keiyakushubetsu = '4'
AND b_t408.choshu_kbn = '2')
相当于
b_t408.kaisha_code = i_kaisha_code
AND b_t408.keijonengetsu = i_batch_shori_ym
AND b_t408.sousai_haifu_kbn = '1'
AND b_t408.syukei_kbn = '0'
AND b_t408.keijoshiharai_kbn = '1'
AND b_t408.keiyakushubetsu = '2'
OR b_t408.kaisha_code = i_kaisha_code
AND b_t408.keijonengetsu = i_batch_shori_ym
AND b_t408.sousai_haifu_kbn = '1'
AND b_t408.syukei_kbn = '0'
and b_t408.keijoshiharai_kbn = '2'
AND b_t408.keiyakushubetsu = '1'
OR b_t408.kaisha_code = i_kaisha_code
AND b_t408.keijonengetsu = i_batch_shori_ym
AND b_t408.sousai_haifu_kbn = '1'
AND b_t408.syukei_kbn = '0'
and b_t408.keijoshiharai_kbn = '1'
AND b_t408.keiyakushubetsu = '4'
AND b_t408.choshu_kbn = '2'

makeitbetter 2005-09-26