Oracle unique index

Introduction to Oracle UNIQUE index A unique index ensures that no two rows of a table have duplicate values in the indexed column (or columns). Oracle Database enforces a UNIQUE key or PRIMARY KEY integrity constraint on a table by creating a unique index on the unique key or primary key. Unique indexes guarantee that no two rows of a table have . Creating a Function-Based.

At one point in the book, while talking about indices, the author says that a unique index is . This Oracle tutorial explains how to create, rename and drop indexes in. UNIQUE : It indicates that the combination of values in the indexed columns must be . We can do this with a function-based index. The following makes use of NVL2() which, as you know, returns one value if the expression is not . What-is-a-unique-index. This article shows a working example of a conditional unique index on . If I load a table with unique values, but I make the index as non- unique , how will Oracle SQL read the data blocks? Is there any difference between a unique and . For example, at times Oracle 10g may not drop the associated index for a primary key or unique constraint that has been dropped.

The CREATE INDEX statement is used to create indexes in tables. Enterprise-ready and Oracle compatible. The key field(s) for the index are specified as column names, or alternatively as expressions written in parentheses.

When creating a primary key or unique constraint, Oracle will automatically create a unique index on that column.