Gk Questions with AnswersSql Interview Question and Answers
| 71. | What is UNIQUE KEY constraint? |
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| A UNIQUE constraint enforces the uniqueness of the values in a set of columns, so no duplicate values are entered. The unique key constraints are used to enforce entity integrity as the primary key constraints. | |
| 72. | What is NOT NULL Constraint? |
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| A NOT NULL constraint enforces that the column will not accept null values. The not null constraints are used to enforce domain integrity, as the check constraints. | |
| 73. | What is meant by query optimization? |
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| The phase that identifies an efficient execution plan for evaluating a query that has the least estimated cost is referred to as query optimization. | |
| 74. | What is meant by embedded SQL? |
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| They are SQL statements that are embedded with in application program and are prepared during the program preparation process before the program is executed. | |
| 75. | What is File Manager? |
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| It is a program module, which manages the allocation of space on disk storage and data structure used to represent information stored on a disk. | |