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You can prevent duplicate values in a field in an Access table by creating a unique index. A unique index is an index that requires that each value of the indexed field is unique.
Show Relationship and Index information for Access using a handy form and module you can import into any database. Development Goto Top Data Dictionary
Create an index. To create an index on an existing table, you use a CREATE INDEX command. A CREATE INDEX command has the following syntax: CREATE [UNIQUE] INDEX index_name ON table (field1 [DESC][, field2 [DESC], ...]) [WITH {PRIMARY | DISALLOW NULL | IGNORE NULL}]
This article introduces indexes and covers how to decide which fields to index, and how to create, delete, or change an index. It also explains the conditions under which Access automatically creates indexes.
13 Μαρ 2017 · Turns out you can create a multi-column unique index on an MS access database, but it's a little crazy if you want to do this via the GUI. There's also a limitation; you can only use 10 columns per index.
Here’s an example to create a Unique index: CREATE UNIQUE INDEX Emp_Phone_IDX ON Employees (emp_phone); There are several other options to the create index statement – we have shown the common options. One powerful feature of the create index statement is to create an index on an ODBC linked table.
20 Φεβ 2013 · CREATE INDEX index_name ON table_name (column_name) Unless you specifically ask that the index be unique, it will allow duplicates. The index can be created using the query design window or in VBA.
