value IN (SELECT primary_key FROM single_table WHERE some_expr) unique_subquery是一个索引查找函数,可以完全替换子查询,效率更高。 (8).index_subquery 该联接类型类似于unique_subquery。可以替换IN子查询,但只适合下列形式的子查询中的非唯一索引: value IN (SELECT key_column FROM single_table WHERE some...
Hash JoinhjoinAlso used for inner joins and left and right outer joins and typically faster than a nested loop join. Hash Join reads the outer table, hashes the joining column, and finds matches in the inner hash table. Step can spill to disk. (Inner input of hjoin is hash step which...
This is a modal window. No compatible source was found for this media. addr opcode p1 p2 p3 --- --- --- --- --- 0 Goto 0 19 1 Integer 0 0 2 OpenRead 0 8 3 SetNumColu 0 5 4 Rewind 0 17 5 Column 0 4 6 RealAffini 0 0 7 Integer 20000 0 8 Lt 357 16 collseq(BI ...
Scans all the block in the index Rows are not returned in sorted order Introduced in 7.3 and requires V733_PLANS_ENABLED=TRUE and CBO may be hinted using INDEX_FFS hint uses multiblock i/o can be executed in parallel can be used to access second column of concatenated indexes. This is b...
An additional column called A-Rows, which stands for actual rows returned, will appear in the plan. 9 THE ORACLE OPTIMIZER EXPLAIN THE EXPLAIN PLAN SQL> SELECT /*+ GATHER_PLAN_STATISTICS */ employee_id, last_name, job_id 2 FROM employees 3 WHERE job_id='AD_VP'; SQL> SELECT plan_...
Debugging SQL performance using query execution plans to verify index usage in MySQL, PostgreSQL, SQL Server and the Oracle database.
Cause: A materialized view with PL/SQL functions in its definition cannot be used for query rewrite when query rewrite integrity is set to ENFORCED. Action: Consider running the query in STALE TOLERATED mode. QSM-01031 materialized view, string, is stale in TRUSTED integrity mode Cause: A st...
=UNIQUE(RANDARRAY(100,1,9788723527370120,9788723527370990,TRUE)) in a clean sheet at a1 cell. Am i doing something wrong? Ohayonson No, it appears to be a bug. Paste the formula into any other cell - it should work. After that it should work in A1 too....
Add months to GETDATE() function in sql server Add new row to datagridview one by one dynamically Add Node existing XML file Add one Column runtime to datagrid view at specific index in C# Add picture into specified Excel cell Add registry values in setup project ADD Root Node to XML ...
A column-organized sort is typically executed in parallel using multiple database agents and can use different methods to distribute the data among the agents, depending on the semantics of the SQL statement. The type of parallel sorting method is indicated by the SORTTYPE argument of the SORT ...