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SQL interview questions

SQL interview questions.

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  • 1.

    Define a temp table

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  • 2.

    What is a view?

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  • 3.

    What is PRIMARY KEY?

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  • 4.

    What is blocking?

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  • 5.

    What is Normalization?

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  • 6.

    What is the difference between WHERE clause and HAVING clause?

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  • 7.

    What is DEFAULT?

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  • 8.

    What is FOREIGN KEY?

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  • 9.

    What’s the difference between a local temp table and a global temp table?

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  • 10.

    How can a column with a default value be added to an existing table?

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  • 11.

    Is table size reduced, when you delete data from the table?

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  • 12.

    Define ACID Properties

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  • 13.

    Discuss INNER JOIN ON vs WHERE clause

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  • 14.

    What is the difference between “INNER JOIN” and “OUTER JOIN”?

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  • 15.

    What is the difference between JOIN and UNION?

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  • 16.

    What is the difference between UNION and UNION ALL?

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  • 17.

    What are the advantages of using Stored Procedures?

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  • 18.

    How do I perform an IF…THEN in an SQL SELECT?

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  • 19.

    What is the difference between inner and outer join?

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  • 20.

    Describe the difference between truncate and delete

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  • 21.

    What is Denormalization?

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  • 22.

    What are the difference between clustered and a non-clustered index?

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  • 23.

    How a database index can help performance?

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  • 24.

    What is a cursor how does it work?

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  • 25.

    What are row constructors?

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  • 26.

    Explain Function vs. Stored Procedure in SQL Server

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  • 27.

    What is collation?

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  • 28.

    Finding duplicate values in a SQL table

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  • 29.

    How to select first 5 records from a table?

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  • 30.

    How does a hash table index work?

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  • 31.

    How do I UPDATE from a SELECT in SQL Server?

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  • 32.

    What is a filegroup?

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  • 33.

    What is the cost of having a database index?

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  • 34.

    How does truncate and delete operation effect Identity?

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  • 35.

    What are DMV's and DMF's?

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  • 36.

    How does B-trees index work?

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  • 37.

    How deadlock is resolved?

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  • 38.

    What are statistics?

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  • 39.

    What is a linked server?

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  • 40.

    Explain the difference between exclusive lock and update lock

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  • 41.

    What is the difference among UNION, MINUS and INTERSECT?

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  • 42.

    How can we transpose a table using SQL (changing rows to column or vice-versa) ?

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  • 43.

    What's the difference between a primary key and a unique key?

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  • 44.

    Name types of Triggers

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  • 45.

    Explain a usage difference between user defined functions and stored procedures

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  • 46.

    What is Optimistic Locking and Pessimistic locking?

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  • 47.

    Select first row in each GROUP BY group (greatest-n-per-group problem)?

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  • 48.

    How does database indexing work?

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  • 49.

    What are some other types of indexes?

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  • 50.

    Name some disadvantages of a hash index

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  • 51.

    How does primary key constraint and unique key constraint effect null?

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  • 52.

    How can I do an UPDATE statement with JOIN in SQL?

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  • 53.

    How to generate row number in SQL Without ROWNUM

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  • 54.

    What would happen without an index?

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  • 55.

    Delete duplicate values in a SQL table

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  • 56.

    Insert results of a stored procedure into a temporary table

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