共返回1 行记录,花费 5 ms。 2. 场景解析 从查询条件中可以看出 token 和 uid 过滤性都非常好,但是由于使用了 or, 需要采用 index merge 的方法才能获得比较好的性能。但在实际执行过程中MySQL优化器默认选择了使用registrationId 上的索引,导致 SQL 的性能很差。 3. 场景优化 我们将SQL改写成union all的形式。
As a developer you must be aware that SQL Server does not do short-circuiting like it is done in other programming languages and there's nothing you can do to force it to. sql-server sql-server-2008 t-sql optimization condition Share Improve this question Follow edited Jun ...
SQL的OR运算符用于根据多个条件筛选记录,只要有一个条件为TRUE,就会返回记录。下面是OR运算符的基本语法: 代码语言:sql AI代码解释 SELECTcolumn1,column2,...FROMtable_nameWHEREcondition1ORcondition2ORcondition3...; column1,column2,等是您要选择的列名称。 table_name是您从中选择记录的表的名称。 condition...
https://stackoverflow.com/questions/5639710/union-all-vs-or-condition-in-sql-server-query https://bertwagner.com/2018/02/20/or-vs-union-all-is-one-better-for-performance/ http://sqlserverplanet.com/optimization/using-union-instead-of-or ...
Fixes an issue in which a query returns incorrect results when you use a varchar(max) variable as the search condition in SQL Server 2014 or 2016.
Semaphore timeout: This error points to a timeout condition related to the use of semaphores in the network. The Wait Operation Timed Out: A wait operation has exceeded its allowed time, typically due to network delays. A fatal error occurred while reading the input stream from the ne...
SQL Copy UPDATE table1 set col3 = 'Dallas' where col1 = 3 The log reader generates only the INSERT stored procedure call, since the row didn't previously meet the filter condition. Although an UPDATE operation was performed at the Publisher, only the appropriate commands are app...
AndCondition Class Argument Class BetweenLeafCondition Class BooleanLeafCondition Class Condition Class ConditionTree Class ConstantValue Class ExpressionOperator Enumeration ExpressionValue Class FieldValue Class FilterAction Enumeration FilterRule Class FilterStatement Class FunctionValue Class InputType Class IsNull...
MergeCondition MergeSpecification MergeStatement MessageSender MessageTypeStatementBase MessageValidationMethod MethodSpecifier MigrationState MirrorToClause ModifyFileGroupOption MoneyLiteral MoveConversationStatement MoveRestoreOption MoveToDropIndexOption MultiPartIdentifier MultiPartIdentifierCallTarget Named...
WindowsService_0!16e4!04/16/2024-13:44:38:: e ERROR: Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException: , An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database...