三、使用SQL语句创建和删除约束 约束的目的是确保表中数据的完整性。 常用的约束类型: 主键约束(Primary Key constraint):要求主键列数据唯一,并且不允许为空。 唯一约束(Unique Constraint):要求该列唯一,允许为空,但只能出现一个空值。 检查约束(Check Constraint):某列取值范围显示、格式限制等,如有关年龄的约束。
constraint CK_savingType check(savingType in('活期','定活两便','定期')), constraint DF_openDate default(getDate()) for openDate, --默认约束,当天日期 constraint CK_openMoney check(openMoney>=1), constraint CK_balance check(balance>=1), constraint CK_pass check(len(pass)>=6), constraint...
組件:Microsoft.Data.Schema.ScriptDom.Sql (在 Microsoft.Data.Schema.ScriptDom.Sql.dll 中) 語法 VB複製 '宣告PublicOverridableSubVisit ( _ nodeAsCheckConstraint _ ) 參數 node 型別:Microsoft.Data.Schema.ScriptDom.Sql.CheckConstraint 指定的片段型別。
程序集:Microsoft.Data.Schema.ScriptDom.Sql(在 Microsoft.Data.Schema.ScriptDom.Sql.dll 中) 语法 VB复制 声明PublicOverridableSubExplicitVisit ( _ nodeAsCheckConstraint _ ) 参数 node 类型:Microsoft.Data.Schema.ScriptDom.Sql.CheckConstraint 指定的片段类型。
1、使用sql查询主键的唯一约束当前最大值：select max（id） from table；（id为number类型）select max（to_number(id)） from table;(id为非number类型)2、使用sql查询该表的序列的下一个值 select SEQ.NEXTVAL from dual;（seq是对应表的序列名）3、最后使用PL/SQL客户端编辑序列，将序列的下一...
TSqlFragmentVisitor Constructores Métodos TSqlParser TSqlParserToken TSqlScript TSqlStatement TSqlStatementSnippet TSqlTokenType TSqlTriggerEventGroupHelper TSqlTriggerEventTypeHelper UnaryExpression UnaryExpressionType UniqueConstraintDefinition UniqueRowFilter UnpivotedTableReference UnqualifiedJoin UnqualifiedJoinTyp...
SQL -- Check to see whether this stored procedure exists.IF OBJECT_ID(N'usp_GetErrorInfo', N'P') IS NOT NULLDROPPROCEDUREusp_GetErrorInfo; GO-- Create procedure to retrieve error information.CREATEPROCEDUREusp_GetErrorInfoASSELECTERROR_NUMBER()ASErrorNumber, ERROR_SEVERITY()ASErrorSeverity, ...
In working with our customers, I come across some very interesting patterns in T-SQL. Not all of these patterns are complex on the face of it, but their impact can sometimes be substantial. Here is a simple example to demonstrate what I am referring to: SELECT CASE WHEN EXISTS (SELECT ...
ALTER TABLE t_users DROP FOREIGN KEY uni_t_users_english_name AutoMigrate for table faild. err:Error 1091 (42000): Can't DROP 'uni_t_users_english_name'; check that column/key exists 实际上是没有这个外键的,但依然会drop这个外键。
In sqlcmd move the -Uand -P parameters after the -Q parameter so that the password is at the end of the command. More details here sqlcmd -S MSSQLSERVER$EXPRESS -Q "dbcc checkdb ('master') with DATA_PURITY, NO_INFOMSGS;" -U maintenanceUser -P ""weirdPassword Use EXIS...