select * from all_tab_columns --查询所有用户的表的列名等信息(详细但是没有备注). select * from user_tab_columns --查询本用户的表的列名等信息(详细但是没有备注). --一般使用1: select t.table_name,t.comments from user_tab_comments t --一般使用2: select r1, r2, r3, r5 from (select a...
SELECTName:'SELECT'Description: Syntax:SELECT[ALL | DISTINCT | DISTINCTROW][HIGH_PRIORITY][STRAIGHT_JOIN][SQL_SMALL_RESULT][SQL_BIG_RESULT][SQL_BUFFER_RESULT]SQL_NO_CACHE[SQL_CALC_FOUND_ROWS]select_expr[, select_expr ...][FROM table_references [PARTITION partition_list][WHERE where_condition]...
AI代码解释 SELECTCASEWHENGROUPING(ware_category)=1THEN'商品类别 合计'ELSEware_categoryENDASware_category,CASEWHENGROUPING(registration_date)=1THEN'登记日期 合计'ELSETO_CHAR(registration_date,'YYYY-MM-DD')ENDASregistration_date,SUM(purchase_unit_price)ASpurchase_unit_pricesFROMtbl_wareGROUPBYCUBE(ware...
The query returns data from all rows and columns in the employees table. The asterisk ( *) character is the shorthand for all columns. The following query is equivalent to the one above but uses explicit column names: SELECT EmployeeID, LastName, FirstName, Title, TitleOfCourtesy, BirthDate...
select table_one_field1,table_one_fileld2...from table_one union[all]select table_two_field1,table_two_field2...from table_two; 其中,union、union all、or 三者的区别如下: union表链接后会利用字段的顺序进行排序,以此筛选掉重复的数据行,最后再返回结果 因此,当数据量很大时效率很低 ...
In SQL, theSELECT INTOstatement is used to copy data from one table to another. Example -- copy all the contents of a table to a new tableSELECT*INTOCustomersCopyFROMCustomers; Here, the SQL command copies all data from theCustomerstable to the newCustomersCopytable. ...
CREATE VIEW View1 AS SELECT Colx, Coly FROM TableA, TableB WHERE TableA.ColZ = TableB.Colz; 查询计划中的联接顺序为 Table1、 Table2、 TableA、 TableB、 Table3。解析视图的索引与任何索引相同,仅当查询优化器确定在 SQL Server 的查询计划中使用索引视图有益时,SQL Server 才会选择这样做。索引...
SELECT LastName FROM [KAWLAPTOP\SQLEXPRESS2014].[AdventureWorks2012].[Person].[Person] to do a query. Luckily we typically write queries within the context of one database so we only need to specify the Schema and TableName as so:
SELECTstor_id,qtyFROM(SELECTstor_id,qtyFROMsalesWHEREqty>50)AStemp_table;2、UNION UNION运算符从...
IF NOT EXISTS (SELECTnameFROMsys.databasesWHEREname= N'Library')CREATEDATABASELibrary; 此脚本将创建一个名为Library的新数据库(如果尚不存在)。 新Library数据库显示在数据库列表中。 如果没有立即看到它,请刷新对象资源管理器。 创建表 现在,在Authors数据库中创建Library表。