sql语句select用法详解（SQL statement select usage detailed）.docVIP

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sql语句select用法详解（SQL statement select usage detailed）.doc

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sql语句select用法详解（SQL statement select usage detailed）

sql语句select用法详解（SQL statement select usage detailed） SQL statement select usage detailed SELECT-SQL command detailed Select - SQL command Retrieve data from one or more tables. grammar SELECT [ALL DISTINCT] [TOP nExpr [PERCENT]] | [Alias.] Select_Item [AS Column_Name] [[Alias.], Select_Item, [AS, Column_Name]...] FROM [FORCE] [DatabaseName!]Table [[AS] Local_Alias]! [[INNER LEFT [OUTER] RIGHT [OUTER] | | | FULL [OUTER] JOIN DatabaseName!]Table [[AS] Local_Alias]! [ON JoinCondition... ] [[INTO Destination] | [TO FILE FileName [ADDITIVE] TO PRINTER [PROMPT] | | TO SCREEN]] [PREFERENCE PreferenceName] [NOCONSOLE] [PLAIN] [NOWAIT] [WHERE, JoinCondition, [AND, JoinCondition...] [AND OR FilterCondition [AND OR FilterCondition | |]]]... [GROUP BY GroupColumn [GroupColumn,... [HAVING FilterCondition] [UNION [ALL] SELECT command] [ORDER BY Order_Item [ASC DESC] [ASC | | [Order_Item, DESC]... parameter SELECT In the SELECT clause, specify the fields, constants, and expressions that are included in the query result. ALL The query result contains all rows (including duplicate values). ALL is the default setting. DISTINCT Exclude duplicate rows in query results. Note that each SELECT clause can only be used once, DISTINCT. TOP nExpr [PERCENT] In all records that conform to the query condition, select a specified number or percentage of records. The TOP clause must be used in conjunction with the ORDER BY clause. The ORDER BY clause specifies the number of rows determined by the Top word on the column included in the query result, and the TOP clause selects the first nExpr or nExpr% record based on this sort. You can specify between 1 and 32767 records. Use the ORDER BY clause specifies the sort field, will produce a parallel situation, for example, may have multiple records in their selected fields on the same; therefore, if you specify nExpr for 10, in the query results can be more than 10 records, because there may be several parallel recording position. If the number of rec