表示先走二级索引,再走一级索引找到数据 finds relevant records based on an Index. Index Scans perform 2 read operations: one to read the index and another to read the actual value from the table. 2、顺序扫描 - Seq Scan Node finds relevant records by sequentially scanning the input record set....
比较常见的范围扫描是带有BETWEEN子句或WHERE子句里有>、>=、<、<=、IS NULL、<=>、BETWEEN、LIKE、IN()等操作符。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECT*FROMtbl_nameWHEREkey_columnBETWEEN10and20;SELECT*FROMtbl_nameWHEREkey_columnIN(10,20,30); 11 index:全索引扫描,和ALL类似,...
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 because we are selecting all of the index. ...
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 ...
advice[1]: [WARNING] The column(s): day(generated by non-deterministic function: CURRENT_TIMESTAMP ) can not satisfy the determinism requirement for correctly processing update message(‘UB’/‘UA’/‘D’ in changelogMode, not ‘I’ only), this usually happens when input node has no upsert...
SQL - NOT EQUAL SQL - IS NULL SQL - IS NOT NULL SQL - NOT NULL SQL - BETWEEN Operator SQL - UNION Operator SQL - UNION vs UNION ALL SQL - INTERSECT Operator SQL - EXCEPT Operator SQL - Aliases SQL Joins SQL - Using Joins SQL - Inner Join SQL - Left Join SQL - Right Join SQL...
EXPLAIN语句返回MYSLQ的执行计划,通过他返回的信息,我们能了解到MYSQL优化器是如何执行SQL语句的,通过分析他能帮助你提供优化的思路。 语法 MYSQL 5.6.3以前只能EXPLAIN SELECT; MYSQL5.6.3以后就可以EXPLAIN SELECT,UPDATE,DELETE EXPLAIN 语法例子: mysql> explain select customer_id,a.store_id,first_name,last_na...
joins the tables in an optimal order. To give a hint to the optimizer to use a join order corresponding to the order in which the tables are namedin a SELECT statement, begin the statement with SELECT STRAIGHT_JOIN rather than just SELECT. (See Section 15.2.13, “SELECT Statement”.) ...
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_...
The following example returns a plan for a statement that joins multiple tables: EXPLAIN SELECT f.film_id, title, name category_name FROM film f INNER JOIN film_category fc ON fc.film_id = f.film_id INNER JOIN category c ON c.category_id = fc.category_id ORDER BY title; The output...