SQL 複製 -- Create table `person` > CREATE TABLE person (name STRING , age INT COMMENT 'Age column', address STRING); -- Returns column metadata information for a simple select query > DESCRIBE QUERY SELECT age,
Query information about a mapping table. Command syntax DESCRIBEtable_name; Examples The following sample code shows how to query the information about the mapping table named mytable: DESCRIBEmytable; Sample output: +---+---+---+---+---+ | Field | Type | Null | Key | Extra | +-...
You can execute theSHOW TABLESstatement to query mapping tables in the current database. Query information about tables You can execute theDESCRIBEstatement to query information about a table, such as the field names and field types. Query index information about tables ...
Azure SQL 数据库提供了名为“查询性能见解”的工具,管理员可以通过该工具快速识别成本高昂的查询。 可以在 Azure SQL 数据库主边栏选项卡中的“智能性能”部分导航到“查询性能见解”。 启动查询性能见解时,你会发现三个按钮,可以用它们筛选长期运行的查询、占用资源最多的查询或自定义筛选器。 默认值为“...
In these edge cases, use the RawSQL expression. For example: >>> from django.db.models.expressions import RawSQL >>> queryset.annotate(val=RawSQL("select col from sometable where othercol = %s", (someparam,))) These extra lookups may not be portable to different database engines (...
Query expressions describe a value or a computation that can be used as part of an update, create, filter, order by, annotation, or aggregate. When an expression outputs a boolean value, it may be used directly in filters. There are a number of built-in expressions (documented below) that...
SQL SQL DESCRIBEemployees_table_vw Scala Scala employees_table.printSchema You can run queries against this JDBC table: Python Python display(employees_table.select("age","salary").groupBy("age").avg("salary")) SQL SQL SELECTage,avg(salary)assalaryFROMemployees_table_vwGROUPBYage ...
You can use theindex metricsto identify which indexes are used for each query and if there are any missing indexes that would improve query performance. Query execution metrics Detailed metrics are returned for each query execution in theDiagnosticsfor the request. These metrics describe where time...
New naming schema for Microsoft SQL Server software update packages For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: 824684 Description of the standard terminology that is used to describe Microsoft software up...
New naming schema for Microsoft SQL Server software update packages For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: 824684 Description of ...