8-Outer Join Between Multiple Tables 多表外连接 9-Self Outer Joins自外连接 10-the USING Clause 子句 11-Natural Joins自然连接 12-Cross Joins交叉连接 13-Unions 联合 在多张表格中检索数据 1-Inner Joins 内连接 / JOIN ON customers 和 orders在不同表格 因为customers的地址、手机会经常更改,如果orders...
od.SalesOrderID = o.SalesOrderID GROUP BY OrderDate, ProductID; GO -- Create an index on the view CREATE UNIQUE CLUSTERED INDEX IDX_V1 ON Sales.vOrders (OrderDate, ProductID); GO -- This query can use the indexed view even though the view is -- not specified in the FROM clause. ...
Remember, the WHERE clause can also be used to filter text results, such as names or countries. SELECT title FROM films WHERE country='China'; 注意就是一定要用单引号 select*from films where certification='R'; WHERE AND Often, you'll want to select data based on multiple conditions. You ...
4. Using HAVING with GROUP BY on Multiple Columns We can use the HAVING clause to filter groups based on aggregate values after grouping by multiple columns. In particular,it allows for more complex conditions on the aggregate results. Let’s extend the previous example where we grouped by bot...
Using DISTINCT on all columns of a table ensures that only completely unique rows, without any duplicates, are included in the result set. 6.Can we filter the results when using DISTINCT on multiple columns? Yes, we can filter the results using a WHERE clause in conjunction with DISTINCT to...
Updating columns by using a two-way assignment such asUPDATE T1 SET @v = column_name = <expression>can produce unexpected results because the live value of the variable can be used in other clauses such as theWHEREandONclause during statement execution instead of the ...
第一部分:基础——增删查改【第一章】做好准备 Getting Started (时长25分钟)【第二章】在单一表格中检索数据 Retrieving Data From a Single Table (时长53分钟)【第三章】在多张表格中检索数据 Retrieving Data From Multiple Tables (时长1小时2分)【第四章】插入、更新和删除数据 Inserting, Updating, an...
The MODEL clause defines a multidimensional array by mapping the columns of a query into three groups: partitioning, dimension, and measure columns. These elements perform the following tasks:Partitions define logical blocks of the result set in a way similar to the partitions of the analytical ...
a matching hint must also be specified as a query hint. Specify the matching hint as a query hint by usingTABLE HINTin theOPTIONclause. This specification preserves the query's semantics. For example, if the query contains the table hintNOLOCK, theOPTIONclause in the@hintsparameter of the ...
Using the RETURN Statement TheRETURNstatement immediately ends the execution of a subprogram and returns control to the caller. Execution continues with the statement following the subprogram call. (Do not confuse theRETURNstatement with theRETURNclause in a function spec, which specifies the datatype...