optimize_aggregated_query(). */ bool JOIN::select_count{false}; (2)SQL引擎层在生成执行计划阶段,判断变量“JOIN::select_count”的值,如果变量值为TRUE,则生成并行COUNT算子“UnqualifiedCountIterator”,用户可以通过“EXPLAIN FORMAT=TREE”或“EXPLAIN ANALYZE”命令查看执行计划,如果包含“Count rows”关键字说...
|executing| 0.000019 |0.000011| 0.000002 |0| 0 |0| 0 |0| 0 |0| 0 |0| exec |sql_executor.cc| 119 ||end|0.000003| 0.000002 |0.000001| 0 |0| 0 |0| 0 |0| 0 |0| 0 |handle_query| sql_select.cc |199| |queryend| 0.000009 |0.000008| 0.000002 |0| 0 |0| 0 |0| 0 |0|...
SET STATISTICS IO, TIME ON; --turn on io and time stats --clear the procedure cache for the WideWorldImporters DB ALTER DATABASE SCOPED CONFIGURATION CLEAR PROCEDURE_CACHE; -- Query with EXISTS -- Query with COUNT(*) -- Query with DISTINCT ...
896 Count(*) vs Count(1) - SQL Server 19 Count(*) vs Count(id) speed 9 Most efficient way to count rows of a query 3 SQL function to get count of how many times string appears in column? -2 SQL Server count(column) query 0 Counting items or incrementing a number? 1 SQL...
(*) as cnt from pg_partition p, pg_namespace n, pg_class r where p.parentid = r.oid and r.relnamespace = n.oid and r.relname = 'test_table' and n.nspname = 'test_schema' and p.parttype = 'p'; QUERY PLAN --- Aggregate (cost=106.15..106.16 rows=1 width=8) -> Nested...
MariaDB [my_database]> SELECT SQL_NO_CACHE COUNT(*) FROM my_table_partitioned PARTITION(p1); +---+ | COUNT(*) | +---+ | 20000200 | +---+ 1 row in set (7.39 sec) MariaDB [my_database]> SHOW PROFILE FOR QUERY 1; +---+---+ | Status | Duration...
optimize_aggregated_query(). */ bool JOIN::select_count{false}; (2)SQL引擎层在生成执行计划阶段,判断变量“JOIN::select_count”的值,如果变量值为TRUE,则生成并行COUNT算子“UnqualifiedCountIterator”,用户可以通过“EXPLAIN FORMAT=TREE”或“EXPLAIN ANALYZE”命令查看执行计划,如果包含“Count rows”关键字说...
Gain the SQL skills to interact with and query your data. Start Learning for Free Count rows that match a condition using COUNT() with CASE WHEN The COUNT(CASE WHEN condition THEN column END) syntax allows us to calculate the number of rows that match a condition. For example, in the ...
sql_authorization.cc|809||Opening tables|0.000015|0.000008|0.000007|0|0|0|0|0|0|0|0|0|open_tables|sql_base.cc|5781||init|0.000018|0.000009|0.000008|0|0|0|0|0|0|0|4|0|handle_query|sql_select.cc|128||System lock|0.000007|0.000004|0.000004|0|0|0|0|0|0|0|0|0|mysql_lock_tables...
【1】Here is a simple count query: === SELECT SQL_NO_CACHE count(*) FROM fees WHERE 1 = 1 AND flag = 0 AND bmonth = '201906'; 【2】Query result: +---+ | count(*) | +---+ | 1021863 | +---+ 1 row in set, 1 warning...