https://dev.mysql.com/doc/refman/5.7/en/explain-output.htmlhttps://dev.mysql.com/doc/refman/8.0/en/explain-output.html Optimizing Queries with EXPLAINThe EXPLAIN statement provides information about how MySQL executes statements: EXPLAIN语句提供了MySQL如何执行语句的信息: EXPLAIN works with SELECT, ...
This indicates that the SQL statement uses the nested loop join. Cross join In Hologres V3.0 and later, a cross join is used as an optimized implementation of a nested loop join in scenarios such as non-equivalent joins that involve small tables. In a nested loop join, a row of data ...
JOINS: Amazon Redshift uses different join operators based on the physical design of the tables being joined, the location of the data required for the join, and specific attributes of the query itself. Subquery Scan -- Subquery scan and append are used to run UNION queries. Nested Loop n...
Consider the statement:int a= 10,20,30;It is a declaration with initialization statement and here comma is a separator and we cannot use values like this. This will be correct output (which is a compile time error): main.cpp: In function ‘int main()’: main.cpp:5:12: error: expect...
"using_join_buffer": "Block Nested Loop", "attached_condition": "(`test`.`t1`.`f1` = `test`.`t1`.`f1`)" } } ] } } EXPLAIN FORMAT=JSON FOR CONNECTION 'SELECT * FROM t1 UNION ALL SELECT * FROM t1 ORDER BY 1' EXPLAIN
The explain plan is produced by the parser. Once the access path has been decided upon it is stored in the library cache together with the statement itself. We store queries in the library cache based upon a hashed representation of that query. When looking for a statement in the library ...
FAST'SLOW' indicates that the scan is expected to progress slowly over the table. For example, if the scan is the outer of a nested loop join). 'FAST' indicates that the scan is expected to progress with higher speed. This information is used to group scans together for efficient sharing...
Clients specify the exact fields required in nested queries, and the server returns optimized payloads containing just those fields. Supports Mutations for modifying data and Subscriptions for real-time notifications. Great for aggregating data from multiple sources and works well with rapidly evolving ...
Here the join operator is a hash-join (other alternatives include nested-loop or sort-merge join). Finally the group-by operator implemented here using hash (alternative would be sort) consumes rows produced by the join-operator, and return the final result set to the end user. 2 THE ...
Partitioning, such as the set of accessed partitions Parallel execution, such as the distribution method of join inputs TheEXPLAINPLANresults let you determine whether the optimizer selects a particular execution plan, such as, nested loops join. It also helps you to understand the optimizer decisi...