4. 临时表存在 tempdb database, 表变量存在 memory database (多的话才会 push to tempdb) 4. 表变量在 query scope 结束后就删除了. 所以我们也不需要手动去删 5. 表变量不能有索引, 但可以有 Primary Key 和 Unique Constraint 6. row < 1000 的情况可以考虑用表变量...
I've tried using this SQL query on an a Stored Procedure on this mode SET tyear = YEAR(CURDATE()); SET @tbl = CONCAT(DATE_FORMAT(CURRENT_TIMESTAMP(), '%Y%m%d%H'),'_',tyear); SET tablename = CONCAT('t_contents_',@tbl,''); SET @GetName = CONCAT(' SELECT GROUP_CONCAT(DISTI...
Also, SQL Server does not maintain statistics on a table variable, and statistics are used heavily by the query optimizer to determine the best method to execute a query. Neither of these restrictions should be a problem, however, as table variables generally exist for a specific purpose and a...
TableVariableTransactionsDoNotSupportParallelNestedTransaction 表变量事务不支持并行嵌套事务。 DMLQueryReturnsOutputToClient DML 查询将输出返回到客户端,并且不可并行化。 MixedSerialAndParallelOnlineIndexBuildNotSupported 单个联机索引生成的串行和并行计划组合不受支持。 CouldNotGenerateValidParallelPlan 验证并行计划失败...
tablevariables don't have distribution statistics. They don't trigger recompiles. In many cases, the optimizer builds a query plan on the assumption that the table variable has no rows. For this reason, you should be cautious about using a table variable if you expect a larger number of ...
FullTextTableReference FunctionCall FunctionCallSetClause FunctionOption FunctionOptionKind FunctionReturnType FunctionStatementBody GeneralSetCommand GeneralSetCommandType GeneratedAlwaysType GenericConfigurationOption GetConversationGroupStatement GlobalFunctionTableReference GlobalVariableExpression GoToStatement Grand...
table_type_definition与在CREATE TABLE 中定义表时所用的信息子集相同的信息子集。 表声明包括列定义、名称、数据类型和约束。 允许的约束类型仅为 PRIMARY KEY、UNIQUE KEY 和 NULL。有关语法的详细信息,请参阅 CREATE TABLE (Transact-SQL) 、CREATE FUNCTION (Transact-SQL) 和DECLARE @local_variable (Transact...
A where clause in the outer-most query sets a constraint on rows returned from derived table. The constraint is that the first character of the name field from the derived table match one of the id column values in the @listOfAlphabetIDs table variable. ...
SQL_ATTR_USE_BOOKMARKS語句屬性已設定為 SQL_UB_VARIABLE,且SQL_ATTR_CURSOR_TYPE語句屬性已設定為驅動程式不支援書簽的資料指標類型。 HYT00 逾時已超過 在資料來源傳回要求的結果集之前,查詢逾時期限已過期。 逾時期間是透過 SQLSetStmtAttr 來設定,SQL_ATTR_QUERY_TIMEOUT。 HYT01 已超過連線逾時 ...
-- 定义变量SET@var1=0;-- 将查询结果赋给变量SELECTCOUNT(*)INTO@var1FROMtable_nameWHEREcolumn_name='value';-- 使用变量SELECT@var1; 1. 2. 3. 4. 5. 6. 7. 8. 在上面的示例中,首先我们定义了一个变量@var1,并初始化为0。然后,我们执行了一个查询语句,将查询结果赋给变量@var1。最后,我们...