更新此列时更新其他列的值答案

【问题标题】：Update value of other column on update of this column更新此列时更新其他列的值
【发布时间】：2019-01-20 09:07:33
【问题描述】：

我有疑问，如何在 Intersystems Cache 中执行触发器之类的操作。情况：例如，我有带有属性（列）的表 X 值A，值B 我想在 UPDATE 更改 valueA 时更新 valueB。我已经定义了全局变量 ^VALUEBGENER 并使用它来增加它的 $SEQ 函数，我的想法是：

Class User.X Extends %Persistent [ ClassType = persistent, DdlAllowed, Final, Owner = {_SYSTEM}, ProcedureBlock, SqlRowIdPrivate, SqlTableName = X]
{
    Property VALUEA As %Library.String(MAXLEN = 8) [ Required,SqlColumnumber = 1];
    Property VALUEB As %Library.Integer(MAXVAL = 2147483647, MINVAL = -2147483648) [ Required,SqlColumnNumber = 1,SqlComputed,SqlColumnumber = 2, SqlComputeCode = {SET {valueB}=$SEQ(^VALUEBGENER)}, SqlComputeOnChange = %%UPDATE];
}

但它不起作用，当我改变 valuea 但它在我改变 valueb 时起作用，有什么想法吗？附言抱歉英语不好

【问题讨论】：

标签： intersystems-cache intersystems intersystems-cache-studio

【解决方案1】：

可以通过添加触发器和SqlCompute来实现

    Class User.X Extends %Persistent [ ClassType = persistent, DdlAllowed, Final, Owner = {_SYSTEM}, ProcedureBlock, SqlRowIdPrivate, SqlTableName = X]
    {
        Property VALUEA As %Library.String(MAXLEN = 8) [ Required, SqlComputed,SqlColumnumber = 1];
        Property VALUEB As %Library.Integer(MAXVAL = 2147483647, MINVAL = -2147483648) [ Required,InitialExpression=0,SqlColumnNumber = 2, SqlComputeCode = {SET {*}=$SEQ(^VALUEB)}, SqlComputeOnChange = %%UPDATE ];
        Trigger[Event=Update]{
           NEW valuebx
           new rowid
           set rowid={ID}
           SET valuebx= 0
           // {fieldname*C} evaluates to 1 if the field has been changed and 0 
           if({VALUEA*C}=1){
             // we trigger sql computeCode and inc of global variable by update
             //and it doesnt matter what is here in :valuebx
               &sql(update x set valueb=:valuebx WHERE ROWID=:rowid)
           }
        }
    }

【讨论】：