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iceice
Starting Member
5 Posts |
 Posted - 2012-05-02 : 10:04:32
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| table has primary key column and "orderid" nvarchar(30) column. table has many records. "orderid" column must be unique.how to set this column as unique? |
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robvolk
Most Valuable Yak
15732 Posts |
Posted - 2012-05-02 : 10:35:38
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| If it's set at the primary key it's already unique. |
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iceice
Starting Member
5 Posts |
Posted - 2012-05-02 : 10:46:05
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| primary key column and "orderid" column are different. "orderid" column has null values too. |
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robvolk
Most Valuable Yak
15732 Posts |
Posted - 2012-05-02 : 11:59:56
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Ah, misread the question. You can't put a unique constraint on orderid if it has multiple nulls. You either have to update them to be unique, delete them from the table, or create a unique filtered index:CREATE UNIQUE INDEX ix_UNQ_orderID ON myTable(orderid) WHERE orderid IS NOT NULL This will work on SQL Server 2008 or higher. |
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unique key to existing column