ISNULL(baset.[name], N'') AS [SystemType], CAST(CASE WHEN baset.[name] IN (N'char', N'varchar', N'binary', N'varbinary', N'nchar', N'nvarchar') THEN clmns.prec ELSE clmns.length END AS int) AS [Length], CAST(clmns.xprec AS tinyint) AS [NumericPrecision], CAST(clmns....
In this article, we are going to learnhow to write a SQL Query to add primary key to a column? Submitted byManu Jemini, on March 14, 2018 Primary key:This key is used to define the uniqueness of column as there always should be a unique row of data for this column. ...
to-number to-date date-add to-string wrap-string split 使用技巧 使用注释 配置文件 参与贡献 相关链接 DSQL 简介 DSQL 的全称是动态结构化查询语言(Dynamic Structured Query Language),他是一种对结构化查询语言(SQL)的一种扩展。DSQL 基于DSL实现,并在其上封装了配置工厂,可轻松管理和解析复杂的 DSQL。
toList(); -- 第1条sql数据 SELECT t1.`value1` AS `value1`, t1.`value2` AS `value2`, t1.`value3` AS `value3` FROM (SELECT t.`title` AS `value1`, SUM(t.`star`) AS `value2`, MAX(t.`create_time`) AS `value3` FROM `t_blog` t WHERE t.`deleted` = false AND t.`...
SQL Server 2016 (13.x) 藉由將字串數據行的述詞向下推送至 SCAN 節點,大幅改善了使用字串型數據行的分析查詢效能。 String predicate pushdown leverages the primary/secondary dictionary created for columns to improve the query performance. 例如,請考慮數據列群組內包含100個相異字串值的字串資料行區段。
There is an IMO big caveat of bulk_create(): It does not set primary key of objects it creates. In my current project, using bulk_create would improve performance, but as I often need an id of the newly created objects, I have to save them one by one. ...
Prior to SQL Server 2022 (16.x), Query Store hints can be applied against the primary replica of an availability group. Starting with SQL Server 2022 (16.x), when Query Store for secondary replicas is enabled, Query Store hints are also replica-aware for secondary replicas in availability ...
That is, we useYii::app()->dbto get the DB connection, and then callCDbConnection::createCommand()to create the needed command instance. Note that instead of passing a whole SQL statement to thecreateCommand()call as we do inData Access Objects, we leave it empty. This is because we ...
然后一般我们也会使用Sping-Data-jpa去作为持久层就是开发,这个就相当于解放了双手,真的是大部分的数据操作都是可以无配置实现,并且做多表操作,级联操作也很方便,如果有需要自己写Sql配置的,也可以使用@Query注解方便的进行配置,可以说,jpa的开发效率确实很高,但缺点就是操作相对没有那么灵活,如果数据量庞大,还是...
ER_CANT_GET_WD 1014 ER_CANT_LOCK 1015 ER_CANT_OPEN_FILE 1016 ER_FILE_NOT_FOUND 1017 ER_CANT_READ_DIR 1018 ER_CANT_SET_WD 1019 ER_CHECKREAD 1020 ER_DISK_FULL 1021 ER_DUP_KEY 1022 ER_ERROR_ON_CLOSE 1023 ER_ERROR_ON_READ 1024 ...