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SQL Interview Questions and Answers

  Difficulty Level: AllBeginnerIntermediateExperienced/Expert

Ques 1. What does one do when one is rightsizing ?

Ques 2. What does the term downsizing refer to ?

Ques 3. What is event trigger ?

Ques 4. Why do stored procedures reduce network traffic ?

Ques 5. What are the types of processes that a server runs ?

Ques 6. What is a event handler ?

Ques 7. What is an integrity constraint ?

Ques 8. What are the various uses of database triggers ?

Ques 9. What is a transaction ?

Ques 10. Why are the integrity constraints preferred to database triggers ?

Ques 11. Why is it better to use an integrity constraint to validate data in a table than to use a stored procedure?

Ques 12. What are the three components of a client server model ?

Ques 13. What are the advantages of client/server model?

Ques 14. What are the disadvantages of the client/server model ?

Ques 15. What are the different topologies available for network ?

Ques 16. What is the first work of Client process ?

Ques 17. What are the responsibilities of a Server ?

Ques 18. In a Client/Server context, what does API (Application Programming Interface) refer to ?

Ques 19. Give some examples of standard API??

Ques 20. What is the main advantage of developing an application using an API ?

Ques 21. What is the main disadvantage of developing an application using an API ?

Ques 22. Why is an event driven program referred to a passive program ?

Ques 23. What are the four types of events ?

Ques 24. What is the difference between file server and a database server ?

Ques 25. What is inheritance ?

Ques 26. What are the two components of ODBC ?

Ques 27. What is the function of a ODBC manager ?

Ques 28. What is the function of a ODBC Driver ?

Ques 29. What description of a data source is required for ODBC ?

Ques 30. How to Retrieve Warnings?

Ques 31. What are stored procedures? How is it useful?

Ques 32. What is SQL?

Ques 33. SQL*Plus

Ques 34. NVL

Ques 35. Date Functions

Ques 36. Character Functions


Ques 38. COLUMN

Ques 39. BREAK

Ques 40. COMPUTE

Ques 41. SET

Ques 42. SPOOL

Ques 43. JOIN

Ques 44. Union

Ques 45. Intersect

Ques 46. Minus

Ques 47. Correlated Subquery

Ques 48. Multiple columns

Ques 49. Sequences

Ques 50. Synonyms

Ques 51. Indexes

Ques 52. Data types

Ques 53. Order of SQL statement execution

Ques 54. Transaction

Ques 55. Commit

Ques 56. Posting

Ques 57. Rollback

Ques 58. Savepoint

Ques 59. Set Transaction

Ques 60. Locking

Ques 61. Consistency

Ques 62. Integrity

Ques 63. Deadlock

Ques 64. Mutating Table

Ques 65. SQL*Loader

Ques 66. The most important DDL statements in SQL are:

Ques 67. Operators used in SELECT statements.

Ques 68. SELECT statements:

Ques 69. The INSERT INTO Statements:

Ques 70. The Update Statement:

Ques 71. The Delete Statements:

Ques 72. Sort the Rows:

Ques 73. The IN operator may be used if you know the exact value you want to return for at least one of the columns.

Ques 74. BETWEEN ... AND

Ques 75. What is the use of CASCADE CONSTRAINTS?

Ques 76. Why does the following command give a compilation error?

Ques 77. Which system tables contain information on privileges granted and privileges obtained?

Ques 78. Which system table contains information on constraints on all the tables created?

Ques 79. What is the difference between TRUNCATE and DELETE commands?

Ques 80. State true or false. !=, <>, ^= all denote the same operation?

Ques 81. State true or false. EXISTS, SOME, ANY are operators in SQL?

Ques 82. What will be the output of the following query?

Ques 83. What does the following query do? SELECT SAL + NVL(COMM,0) FROM EMP;

Ques 84. What is the advantage of specifying WITH GRANT OPTION in the GRANT command?

Ques 85. Which command executes the contents of a specified file?

Ques 86. What is the value of comm and sal after executing the following query if the initial value of 'sal' is 10000 UPDATE EMP SET SAL = SAL + 1000, COMM = SAL*0.1;?

Ques 87. Which command displays the SQL command in the SQL buffer, and then executes it?

Ques 88. What command is used to get back the privileges offered by the GRANT command?

Ques 89. What will be the output of the following query?
SELECT DECODE(TRANSLATE('A','1234567890','1111111111'), '1','YES', 'NO' );?

Ques 90. Which date function is used to find the difference between two dates?

Ques 91. What operator performs pattern matching?

Ques 92. What is the use of the DROP option in the ALTER TABLE command?

Ques 93. What operator tests column for the absence of data?

Ques 94. What are the privileges that can be granted on a table by a user to others?

Ques 95. Which function is used to find the largest integer less than or equal to a specific value?

Ques 96. Which is the subset of SQL commands used to manipulate Oracle Database structures, including tables?

Ques 97. What is the use of DESC in SQL?

Ques 98. What command is used to create a table by copying the structure of another table?

Ques 99. TRUNCATE TABLE EMP; DELETE FROM EMP; Will the outputs of the above two commands differ?

Ques 100. What is the output of the following query SELECT TRUNC(1234.5678,-2) FROM DUAL;?

Ques 101. What are the wildcards used for pattern matching.?

Ques 102. What is the parameter substitution symbol used with INSERT INTO command?

Ques 103. What's an SQL injection?

Ques 104. What is difference between TRUNCATE & DELETE ?

Ques 105. What is a join? Explain the different types of joins?

Ques 106. What is the sub-query?

Ques 107. What is correlated sub-query?

Ques 108. Explain CONNECT BY PRIOR?

Ques 109. Difference between SUBSTR and INSTR?


Ques 111. What is ROWID?

Ques 112. What is the fastest way of accessing a row in a table?

Ques 113. What is an integrity constraint?

Ques 114. What is referential integrity constraint?

Ques 115. What is the usage of SAVEPOINTS?

Ques 116. What is ON DELETE CASCADE?

Ques 117. What are the data types allowed in a table?

Ques 118. What is difference between CHAR and VARCHAR2? What is the maximum SIZE allowed for each type?

Ques 119. How many LONG columns are allowed in a table? Is it possible to use LONG columns in WHERE clause or ORDER BY?

Ques 120. What are the pre-requisites to modify datatype of a column and to add a column with NOT NULL constraint?

Ques 121. Where the integrity constraints are stored in data dictionary?

Ques 122. How will you activate/deactivate integrity constraints?

Ques 123. If unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE?

Ques 124. What is a database link?

Ques 125. How to access the current value and next value from a sequence? Is it possible to access the current value in a session before accessing next value?

Ques 126. What is CYCLE/NO CYCLE in a Sequence?

Ques 127. What are the advantages of VIEW?

Ques 128. Can a view be updated/inserted/deleted? If Yes - under what conditions?

Ques 129. If a view on a single base table is manipulated will the changes be reflected on the base table?

Ques 130. Which of the following statements is true about implicit cursors?

Ques 131. Which of the following is not a feature of a cursor FOR loop?

Ques 132. A developer would like to use referential datatype declaration on a variable. The variable name is EMPLOYEE_LASTNAME, and the corresponding table and column is EMPLOYEE, and LNAME, respectively. How would the developer define this variable using referential datatypes?

Ques 133. Which three of the following are implicit cursor attributes?

Ques 134. If left out, which of the following would cause an infinite loop to occur in a simple loop?

Ques 135. Which line in the following statement will produce an error?

Ques 136. The command used to open a CURSOR FOR loop is

Ques 137. What happens when rows are found using a FETCH statement 1. It causes the cursor to close 2. It causes the cursor to open 3. It loads the current row values into variables 4. It creates the variables to hold the current row values

Ques 138. Under which circumstance must you recompile the package body after recompiling the package specification?

Ques 139. Procedure and Functions are explicitly executed. This is different from a database trigger. When is a database trigger executed?

Ques 140. Which Oracle supplied package can you use to output values and messages from database triggers, stored procedures and functions within SQL*Plus?

Ques 141. For this code to be successful, what must be true?

Ques 142. A stored function must return a value based on conditions that are determined at runtime. Therefore, the SELECT statement cannot be hard-coded and must be created dynamically when the function is executed. Which Oracle supplied package will enable this feature?

Ques 143. How to implement ISNUMERIC function in SQL *Plus ?

Ques 144. How to Select last N records from a Table?

Ques 145. What are steps required tuning this query to improve its performance?

Ques 146. What is the difference between Truncate and Delete interms of Referential Integrity?

Ques 147. What does preemptive in preemptive multitasking mean ?

Ques 148. What does the OLTP stands for ?

Ques 149. What is the most important requirement for OLTP ?

Ques 150. In a client server environment, what would be the major work that the client deals with ?

Ques 151. Why is the most of the processing done at the sever ?

Ques 152. What does teh term upsizing refer to ?

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