-- two queries to pull large data datable -- 1) much faster query by using time index SELECT * FROM your table WHERE time > start1 AND time < end1 SELECT * FROM your table WHERE time > start2 AND time < end2 ... ... --rest of timestamps -- 2) much slow query by pulling...
解读Query Block 层次执行计划对应 SQL 有时候会比较复杂,特别是当涉及子查询或者设计多表的时候,但是从优化器的构建思想来看,其实是分层的,每层可以看作是一个简单的 Query Block,每层的构建路径都是相同的,执行计划的展示也是每层构建完之后层层堆叠起来的,而后才是经过逻辑优化,join reorder 等一系列变化来改变...
hasData()) return Status::NeedData; // 如果 state 已经有数据,那么调用 pullData() 方法 // 将数据拉取到 current_chunk 中,并将 has_input 设为 true. current_chunk = input.pull(true); current_block_kind = kind; has_input = true; return Status::Ready; } finished = true; if (!
INSERT INTO test_data VALUES (2, 'diapers'); INSERT INTO test_data VALUES (3, 'beer'); INSERT INTO test_data VALUES (3, 'diapers'); INSERT INTO test_data VALUES (4, 'beer'); INSERT INTO test_data VALUES (4, 'chips'); INSERT INTO test_data VALUES (5, 'beer'); INSERT INTO ...
Connect to and Prepare Data Connect to Your Data Set Up Data Sources Plan the Data Source Relate Your Data Join Your Data Blend Your Data Union Your Data Create a Data Source with Clipboard Data Connect to a Custom SQL Query Use a Stored Procedure Use Recommended Data Source...
对于这条查询 sql ,我们可以认为 x=3 筛选后的结果集肯定是比较小了,因 为是一个精确匹配。如果 select count(*) from table1 where x= 3 出来的结 果比较小的话,time 列再去走索引效果反而差。 所以,对于这种 query,增加 hint no-index:
SQL query stress simulator created by Adam Machanic http://dataeducation.com/sqlquerystress-the-source-code/ - ErikEJ/SqlQueryStress
在Entity Framework 4.1中引入的DbContext API暴露了一些新的方法用于提供透传原生SQL给数据库执行查询和命令,比如Database.SqlQuery<T>, 以及 Database.ExecuteSqlCommand。 这些方法很重要不仅仅因为它们允许你执行自己的原生SQL查询,而且因为它们是当前你可以使用DbContext访问存储过程的主要方法,特别当你使用代码优先的...
继续分析 query_planner:/* * query_planner * Generate a path (that is, a simplified plan) for a basic query, * which may involve joins but not any fancier
sql-query-formatter Star Here are 11 public repositories matching this topic... Language: All Sort: Most stars jOOQ / jOOQ Star 6.2k Code Issues Pull requests Discussions jOOQ is the best way to write SQL in Java mysql java sql orm database code-generator jdbc jpa postgresql oracle sql-...