The following example creates a unique index: CREATE UNIQUE INDEX dept_unique_index ON dept (dname) TABLESPACE indx; Alternatively, you can define UNIQUE integrity constraints on the desired columns. Viewed 57k times 149. Assuming that you need to look up for John Doe’s phone number on a phone book. Ask Question Asked 6 years, 1 month ago. I just added a unique constraint like you're asking for to one of my tables. CREATE INDEX constructs an index on the specified column(s) of the specified relation, which can be a table or a materialized view. A unique index does not allow any duplicate values to be inserted into the table. Unique indexes are used not only for performance, but also for data integrity.
Non-unique indexes do not impose this restriction on the column values. 30. Not having the needed indexes will typically result in high CPU usage in your database server, slow response times, and ultimately unhappy users. Use the CREATE UNIQUE INDEX statement to create a unique index. Indexes are used to retrieve data from the database more quickly than otherwise. How to Create an Index in MySQL Having the right indexes on tables are critical to making your queries performant, especially when your data grows. If you do not care about the name of the index, have Postgres auto-name it: CREATE INDEX ON tbl1 (col1);

(Follows logically.)

Index names cannot be the same as any other index, (foreign) table, (materialized) view, sequence or user-defined composite type in the same schema. The basic syntax is as follows − CREATE UNIQUE INDEX index_name on table_name (column_name); Partial Indexes. Postgres unique constraint vs index. Indexes are primarily used to enhance database performance (though inappropriate use can result in slower performance). For SQL Server 2005 and earlier, you can do it without a view. The users cannot see the indexes, they are just used to speed up searches/queries. Active 7 days ago. Summary: in this tutorial, you will learn about indexes and how to use the PostgreSQL CREATE INDEX statement to define a new index for a table.. Phonebook analogy and index. Two tables in the same schema cannot have an index of the same name. The CREATE INDEX statement is used to create indexes in tables. Just filter a unique index: CREATE UNIQUE NONCLUSTERED INDEX UQ_Party_SamAccountName ON dbo.Party(SamAccountName) WHERE SamAccountName IS NOT NULL; In Lower Versions, A Materialized View Is Still Not Required. CREATE INDEX fake_table_index ON table_name (inactive, column_name); This is more expensive than the filtered index because it indexes all the values of inactive , not just where inactive = 0 .

This also doesn't have the unique constraint that the filtered index does.