This tableis referenced as the child of table in a join that can be pushed down to the NDBkernel. Applies only in MySQL Cluster, when pushed-down joins are enabled. Seethe description of the ndb_join_pushdown serversystem variable for more information and examples. const row not found (JSON...
EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joins using a nested-loop join method. Thismeans that MySQL reads a row from the first ...
We recommend that you prevent non-equivalent joins in SQL statements. The following code provides an example of a nested loop join. BEGIN; CREATE TABLE public.nestedloop_test_1 ( a integer not null, b integer not null ); CALL set_table_property('public.nestedloop_test_1', 'distribution_...
It makes these decisions based on the statistical information it has about your data and by leveraging Oracle database features such as hash joins, parallel query, partitioning, etc. Still it is expected that the optimizer will generate sub-optimal plans for some SQL statements now and then. ...
Example 2: Analyzing Joins Consider a query joining employees and departments tables to retrieve department names along with employee data. Code:> -- Analyze the join performance between employees and departmentsEXPLAINANALYZESELECTe.id,e.name,d.department_nameFROMemployees eJOINdepartments dONe.departmen...
backoff: Contains different types of backoff and the total waiting time of backoff. Insert The execution information of an Insert operator is typically as follows: prepare:109.616µs, check_insert:{total_time:1.431678ms, mem_insert_time:667.878µs, prefetch:763.8µ...
We could represent the joins present in the query using the following schematic: B <---> A <---> C col3=10 col3=5 There are really only 2 ways we can drive the query: via B.col3 or C.col3. We would have to do a Full scan of A to be able to drive off it. This is ...
JOINs Let’s see what the EXPLAIN output of more complex query looks like. We’ll try to find all films released in the year of 2006 where the actor with a last name of ‘MIRINDA’ starred. mysql> EXPLAIN SELECT title, description FROM film AS f JOIN film_actor AS fa ON f.film_id...
EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joins using a nested-loop join method. Thismeans that MySQL reads a row from the first...
12.1.3.1 Using V$SQL_PLAN Views In addition to running the EXPLAIN PLAN command and displaying the plan, you can use the V$SQL_PLAN views to display the execution plan of a SQL statement: After the statement has executed, you can display the plan by querying the V$SQL_PLAN view. V$SQL...