Question

我正在使用Access database，我想将Check Constraint保存为查询。这在Access中是否可能？无论如何，这是我的查询：

ALTER TABLE LEVERANCIER
ADD CONSTRAINT chk_postcode CHECK(
NOT EXISTS(
SELECT levnr, postcode
FROM LEVERANCIER
WHERE Left(postcode, 4) = 5050 OR Woonplaats = "Amsterdam"));

它在AnySQL Maestro中有效，但它在Access中不起作用。

Answer 1

Access数据库引擎支持CHECK约束，但无法从Access中的查询设计器执行创建它们的DDL。必须使用VBA代码和ADO连接创建它们，如下所示：

Option Compare Database
Option Explicit

Public Sub AddCheckConstraint()
    Dim strSql As String
    strSql = _
            "ALTER TABLE LEVERANCIER" & vbNewLine & _
            vbTab & "DROP CONSTRAINT chk_postcode;"
    On Error Resume Next
    CurrentProject.Connection.Execute strSql
    On Error GoTo 0
    strSql = _
            "ALTER TABLE LEVERANCIER" & vbNewLine & _
            vbTab & "ADD CONSTRAINT chk_postcode" & vbNewLine & _
            vbTab & "CHECK (" & vbNewLine & _
            vbTab & vbTab & "NOT EXISTS (" & vbNewLine & _
            vbTab & vbTab & vbTab & "SELECT levnr, postcode " & vbNewLine & _
            vbTab & vbTab & vbTab & "FROM LEVERANCIER " & vbNewLine & _
            vbTab & vbTab & vbTab & "WHERE Left(postcode, 4) = '5050' OR Woonplaats = 'Amsterdam' " & vbNewLine & _
            vbTab & vbTab & ")" & vbNewLine & _
            vbTab & ");"
    CurrentProject.Connection.Execute strSql
End Sub

检查Access中的约束

1 个答案: