{"id":33619,"date":"2023-06-09T11:31:00","date_gmt":"2023-06-09T03:31:00","guid":{"rendered":"https:\/\/docs.pingcode.com\/?p=33619"},"modified":"2023-07-31T00:27:04","modified_gmt":"2023-07-30T16:27:04","slug":"%e6%95%b0%e6%8d%ae%e5%ba%93%e4%b8%ad%e5%85%b3%e7%b3%bb%e4%bb%a3%e6%95%b0%e4%b8%8e%e5%85%b3%e7%b3%bb%e8%bf%90%e7%ae%97%e7%9a%84%e5%8c%ba%e5%88%ab%e6%98%af%e4%bb%80%e4%b9%88","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/33619.html","title":{"rendered":"\u6570\u636e\u5e93\u4e2d\u5173\u7cfb\u4ee3\u6570\u4e0e\u5173\u7cfb\u8fd0\u7b97\u7684\u533a\u522b\u662f\u4ec0\u4e48"},"content":{"rendered":"
\n

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\n
\"\"<\/figure>\n<\/div>\n

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1.\u8303\u56f4\u53d8\u91cf\u5b9a\u4e49<\/p>\n

<Range var definition>::=<\/p>\n

RANGEVAR <range var name> RANGES OVER <relational exp commlist><\/p>\n

2.\u8303\u56f4\u5c5e\u6027\u5b9a\u4e49<\/p>\n

<range attr reference>::=<\/p>\n

<range var name>.<attr reference> [ AS <atrr name> ]<\/p>\n

3.\u5e03\u5c14\u8868\u8fbe\u5f0f<\/p>\n

<boolean exp>::= \u2026 all the usual possibilities, together with: | <quantified boolean exp><\/p>\n

4.\u91cf\u5316\u5e03\u5c14\u8868\u8fbe\u5f0f\uff08\u5b58\u5728\u548c\u5168\u90e8\uff09<\/p>\n

<quantified boolean exp>::=<\/p>\n

EXISTS <range var name>(<boolean exp>)|<\/p>\n

FORALL <range var name>(boolean exp>)<\/p>\n

5.\u5173\u7cfb\u64cd\u4f5c<\/p>\n

<relational operation>::= <proto tuple>[WHERE <boolean exp>]<\/p>\n

6.\u5143\u7ec4\u8868\u8fbe\u5f0f<\/p>\n

<proto tuple> ::= <tuple exp><\/p>\n

\u5ef6\u4f38\u9605\u8bfb\uff1a<\/strong><\/p>\n

\u4e8c\u3001\u4ec0\u4e48\u662f\u6570\u636e\u5e93<\/strong><\/h2>\n

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