SQL规范要求:所有约束(包括:PRIMARY KEY,UNIQUE,FOREIGN KEY,CHECK)属于同一个命名空间(NAMESPACE),在MySQL实现中,所有的约束类型在每个schema (database)内有自己的命名空间。所以,CHECK约束的名称在SCHEMA内必须唯一,也就是说不允许有两张表使用同一个CHECK约束名称。(例外:一个临时表可能使用与非临时表一样的约束...
Check if database exists? Check if Feb-29 is falling between start and end dates Check if file exists then delete it- fix code Check if installed SQL Server is an Eval copy Check if login has db_owner via user mappings on a specific database Check if objects already exist (i.e. FILE...
ALTER TABLE 时的SQL CHECK约束 当表已被创建时,如需在“P_Id”列创建CHECK约束,使用下面的SQL: MySQL/SQL Server/Oracle/MS Access: ALTER TABLE Persons ADD CHECK(P_Id>0) 如需命名CHECK约束,并定义多个列的CHECK约束,使用下面的SQL语法: MySQL/SQL Server/Oracle/MS Access: ALTER TABLE Persons ADD CON...
查询数据库信息查询 MySQL数据库 的版本号 select version();查看当前使用的数据库 select database();查询表结构查询表结构(desc 是 describe 的缩写) desc(或describe) 表名;简单查询查询指定字段的数据( 可以是一个字段,也可以是多个字段,字段之间逗号隔开 ) select 字段1 , 字段2 , 字段3… from 表名;...
c# Check registry if program is installed if yes get install location ? C# Check to make sure first character in a string is a letter C# check username if already exists from database C# Class - USB Port Enabled/Disabled Status Detection C# class for JSON is resulting a Null Reference Exce...
2011 SQL Server MagazineCommunity Choice: Best Free Tool, Gold award “Hands down, one of the best tools out there! If you’re responsible for a database, you should be using Ola’s scripts. It’s very comprehensive, is efficient with resources, has numerous options, and is a brilliant ...
Check for a server name that already exists 示例请求 HTTP HTTP 复制 POST https://management.azure.com/subscriptions/00000000-1111-2222-3333-444444444444/providers/Microsoft.Sql/checkNameAvailability?api-version=2023-08-01 { "name": "server1", "type": "Microsoft.Sql/servers" } 示例响应 状...
$if[[$result-eq 0 ]]thenecho"The database exists"elseecho"The database doesn’t exist"fiCopy 2.2. Using theshow databasesStatement The “use students” SQL statement isn’t the only SQL statement that we can use to check the existence of thestudentsdatabase.We can also use the “show...
We want to know if an index named ix_halp exists on the table agg.FirstNameByYear in theSQLIndexWorkbook database– now renamed to BabbyNames. It does! It was created with this code: CREATENONCLUSTEREDINDEXix_halpONagg.FirstNameByYear (ReportYear) ...
Theto_regclass()function checks if a database object with the specified name exists. If it does, it returns theobject ID; otherwise, it returnsNULL. We can use theCOALESCE()function to convert this result into a boolean value. However,this approach returnstrueif any database object with tha...