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Installation
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How can I make an existing column have a unique constraint
Posted: 6 Sep 01
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1) Make sure that the column only conains unique values
lets assume we are working with a table called t5. it has two columns. id ( the primary key ) and name. To find out if the column contains any duplicate values make the following statements.
select name from t5 ;
select distinct name from t5 ;
IF the row counts are the same then the column contains unique values only.
2) Create a unique index as follows..
alter table t5 add unique ( name ) ;
If you want to give the index a name do it this way...
alter table t5 add unique namedex ( name )
3) Drink a beer
That's it!
* You may optionally drink beer between and during steps one and two. |
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