SQL 型 V3.2.4 开发指南 SQL 语法 普通租户(MySQL 模式) SQL语句 EXPLAIN 更新时间:2025-02-24 23:00:01 描述 该语句用于解释 SQL 语句的执行计划,可以是SELECT、DELETE、INSERT、REPLACE或UPDATE语句。 EXPLAIN与DESCRIBE、DESC互为同义词。 语法 {EXPLAIN|DESCRIBE|DESC}[explain_type]dml_statement;explain_typ...
MaxCompute SQL提供explain语句来分析查询语句或表结构的性能瓶颈。本文介绍explain的功能、命令格式及使用示例。 功能介绍 EXPLAIN语句可以显示MaxCompute SQL对应的DML语句执行计划(执行SQL语义的程序)的结构,帮助您了解SQL语句的处理过程,为优化SQL语句提供帮助。一个查询语句作业会对应多个Job,一个Job对应多个Task。 说明...
The EXPLAIN command will fail if you use it for other SQL commands, such as data definition language (DDL) or database operations. The EXPLAIN output relative unit costs are used by Amazon Redshift to choose a query plan. Amazon Redshift compares the sizes of various resource estimates to ...
If SQL query performance is poor or query results do not meet expectations, you can execute the EXPLAIN and EXPLAIN ANALYZE statements in Hologres to obtain execution plans of query statements. This way, you can optimize query statements or database structures. This topic describes how to execute...
关联的 issue #2857 描述你的变更 规则:扫描行数超过阈值,筛选条件必须带上主键或者索引,名称变更为:扫描行数超过阈值,请检查索引配置取消规则中对SQL执行计划中type类型的检测,转而一旦扫描行数超过阈值就触发规则调整单元测试预期结果 确认项(pr提交后操作) T
The EXPLAIN PLAN statement allows you to submit a SQL statement to Oracle and have the database prepare the execution plan for the statement without actually executing it. The execution plan is made available to you in the form of rows inserted into a special table called a plan table. You...
Explain the IN and LIKE operators as they are used in the where clause of a select statement. How do you use the IN operator in an SQL query? What is the syntax for this operator? How does SQL work? How do you use SQL commands ...
These are the methods under Command Object ExecuteReader : Used to execute SQL Select Command ExecuteScalar : Used to execute SQL Select command which is used to return a single value. Example the group function output ExecuteNonQuery : USed to execute SQL Insert, Delete and Update Commands. ...
Explain how to end the current transaction in Oracle. Following commands could be run to explicitly end the current transaction: a. COMMIT b. ROLLBACK A transaction ends when any of the following actions occurs: 1. A user issues a COMMIT or ROLLBACK statement without a SAVEPOINT clause. ...