(50) )ASBEGINDECLARE@last_child HIERARCHYID; INS_EMP:SELECT@last_child =MAX(EmployeeId)FROMOrg_T1WHEREEmployeeId.GetAncestor(1) = @mgrid;INSERTINTOOrg_T1 (EmployeeId, EmployeeName)SELECT@mgrid.GetDescendant(@las
select A,B,C.. from xx; SELECT title,release_year,country FROM films; select all 选择数据库里全部的列 SELECT*FROM films; SELECT DISTINCT often your results will include many duplicate values. If you want to select all the unique values from a column, you can use the DISTINCT keyword. SE...
6. SELECT子句中避免使用 ‘ * ‘ 当你想在SELECT子句中列出所有的COLUMN时,使用动态SQL列引用 ‘*’ 是一个方便的方法.不幸的是,这是一个非常低效的方法. 实际上,ORACLE在解析的过程中, 会将’*’ 依次转换成所有的列名, 这个工作是通过查询数据字典完成的, 这意味着将耗费更多的时间. 7.减少访问数据库的...
SQL Server automatically assigns unique values for the column. The -E option has a special permissions requirement. For more information, see "Remarks" later in this article. -f format_file Specifies the full path of a format file. The meaning of this option depends on the environment in ...
The threshold is based on the number of rows in the table or indexed view. Query Optimizer checks for out-of-date statistics before it compiles a query and runs a cached query plan. Query Optimizer uses the columns, tables, and indexed views in the query predicate to determine which ...
Specifies that identity value or values in the imported data file are to be used for the identity column. If -E isn't given, the identity values for this column in the data file being imported are ignored, and SQL Server automatically assigns unique values based on the seed and increment ...
/*高效SQL:(索引有效)*/ SELECT * FROM DEPARTMENT WHERE DEPT_CODE >=0;28. 总是使用索引的第一个列如果索引是建立在多个列上,只有在它的第一个列(leading column)被where子句引用时, 优化器才会选择使用该索引。 SQL> create index multindex on multiindexusage(inda,indb);Index created....
[ , ] LASTROW =last_row ] [ [ , ] MAXERRORS =max_errors ] [ [ , ] ORDER ( { column [ ASC | DESC ] } [ ,...n ] ) ] [ [ , ] ROWS_PER_BATCH =rows_per_batch ] [ [ , ] ROWTERMINATOR ='row_terminator' ] [ [ , ] TABLOCK ] [ [ , ] ERRORFILE ='file_name' ...
Cases (1) and (2) allow SQL Server to apply a query predicate to rows from the view to further restrict the rows of the view. Number (3) is a special case where no filtering is needed on the column, so the column needn't appear in the view. If the query contains more than one...
For a DB2 for z/OS server, if a column of the system-period temporal table is defined as ROWID, then the corresponding history column should be defined as ROWID with the same generation attribute (GENERATED ALWAYS or GENERATED BY DEFAULT). ...