Multiple choice technology databases

What is true about UNIQUE KEY? Choose all that apply

  1. Can be defined only on a single column in the table.

  2. Can be defined on a single column or multiple columns in the table.

  3. A UNIQUE index is automatically created once UNIQUE KEY is defined on the table.

  4. A NON-UNIQUE index is automatically created once UNIQUE KEY is defined on the table.

  5. NULL values are NOT acceptable on the columns, which are part of UNIQUE KEY

  6. NULL values are acceptable, which are part of UNIQUE KEY
Reveal answer Fill a bubble to check yourself
B,C,F Correct answer
Explanation

A UNIQUE constraint can be defined on single or multiple columns and automatically creates a unique index to enforce uniqueness. Unlike primary keys, columns with a unique key constraint are permitted to contain NULL values, making the selected options correct.

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