The SELECT identifier. This is the sequential number of the SELECT within the query. The value can be NULL if the row refers to the union result of other rows. In this case, the table column shows a value like <unionM,N> to indicate that the row refers to the union of the rows wi...
it displays the execution plan for the statement executing in the named connection. See Section 8.8.4, “Obtaining Execution Plan Information for a Named Connection”. 当EXPLAIN与FOR CONNECTION connection_id而不是可解释语句一起使用时,它将显示在指定连接中执行的语句的执行计划。参见...
{explainable_stmt | FOR CONNECTION connection_id}方式三: {EXPLAIN | DESCRIBE | DESC} ANALYZE select_statement 参数说明: explain_type: {FORMAT = format_name }format_name: { TRADITIONAL | JSON | TREE } explainable_stmt: {SELECT statement | TABLE statement | DELETE statement | INSERT statement ...
The SELECT identifier. This is the sequential number of the SELECT within the query.The value can be NULL if the row refers to the union result of other rows. In this case, the table column shows a value like <unionM,N> to indicate that the row refers to the union of the rows with...
/* run it (if needed) and produce output */ ExplainOnePlan(plan, into, es, queryString, params, queryEnv, &planduration); }}/* * ExplainOneUtility - * print out the execution plan for one utility statement * (In general, utility statements don't have plans, but there are some * ...
If you query data from a partitioned table, the Seq Scan on Partitioned Table keywords are displayed in the execution plan of the query. You can obtain the number of partitions that are scanned in the query statement from the Partitions selected keywords. Example: Execute the following statem...
such as nested loops and dynamic SQL, especially when addressing performance issues. In the absence of built-in debugging features like breakpoints, developers often resort to inserting manual debug statements or using RAISE NOTICE for logging. While effective, this approach can be...
Can I convert a foreach and if Statement into LINQ? Can i Convert Array to Queue? can i convert from string to guid Can I convert ITextSharp.Text.Image to System.Drawing.Bitmap? Can I do a Visual Basic (VB) Stop in C#? Can I have mutiple app.config files? Can I have two meth...
The 'while' loop can be implemented (in C) as: inti=5; while(i>=0) { printf("%d",i); i--; } where 'i' is the loop variable The 'do-while' loop can be implemented (in C) as: inti=5; do { printf("%d",i); i--; ...
使用Block Nested Loop或Batched Key Access算法提高join的性能。详见javascript:void(0) Using MRR 使用了Multi-Range Read优化策略。详见“Multi-Range Read Optimization” Using sort_union(…), Using union(…), Using intersect(…) 这些指示索引扫描如何合并为index_merge连接类型。详见“Index Merge Optimizatio...