How to constrain that a table gets multiple values in t-sql?

I thought of creating a trigger in t-sql that constrains having multiple values of the same column. It has three unique keys - which needs to be unique. How to get the current row in a t-sql trigger? Is i开发者_运维百科t possible?

If those values are predefined you can create an other table which contain all these unique values and then create FK constraint.

For me it looks like as standard look up table: