Tag: databases

Questions Related to databases

Evaluate these two SQL statements: SELECT last_name, salary , hire_date FROM EMPLOYEES ORDER BY salary DESC; SELECT last_name, salary, hire_date FROM EMPLOYEES ORDER BY 2 DESC; What is true about them

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  1. The two statements produce identical results.

  2. The second statement returns a syntax error

  3. There is no need to specify DESC because the results are sorted in descending order by default

  4. The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement.

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Correct Option: A
Explanation:

To understand these SQL statements, the user needs to know the basic syntax of the SELECT statement and the ORDER BY clause. The SELECT statement retrieves data from one or more tables, and the ORDER BY clause sorts the results in ascending or descending order based on one or more columns' values.

The first SQL statement retrieves the last_name, salary, and hire_date columns from the EMPLOYEES table and sorts the results in descending order based on the salary column's values.

The second SQL statement retrieves the last_name, salary, and hire_date columns from the EMPLOYEES table and sorts the results in descending order based on the second column, which is the salary column.

A. The two statements produce identical results. This is correct because both statements retrieve the same columns and sort the results in descending order based on the salary column's values.

B. The second statement returns a syntax error. This is incorrect because the second SQL statement is syntactically correct and will execute without errors.

C. There is no need to specify DESC because the results are sorted in descending order by default. This is incorrect because the default order is ascending, not descending. If the user wants to sort the results in descending order, they must specify DESC explicitly.

D. The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement. This is incorrect because adding a column alias does not affect the sorting order. The two statements already produce identical results, so there is no need to modify them.

Therefore, the answer is: A. The two statements produce identical results.

You would like to display the system date in the format "Monday, 01 June, 2001". Which SELECT statement should you use?
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  1. SELECT TO_DATE(SYSDATE, 'FMDAY, DD Month, YYYY') FROM dual;

  2. SELECT TO_CHAR(SYSDATE, 'FMDD, DY Month, 'YYYY') FROM dual;

  3. SELECT TO_CHAR(SYSDATE, 'FMDay, DD Month, YYYY') FROM dual;

  4. SELECT TO_CHAR(SYSDATE, 'FMDY, DDD Month, YYYY') FROM dual;

  5. SELECT TO_DATE(SYSDATE, 'FMDY, DDD Month, YYYY') FROM dual;

Show answer
Correct Option: C
Explanation:

To solve this question, the user needs to know the basic SQL functions like TO_CHAR and SYSDATE and their usage and format masks.

Option A: This option is incorrect because it uses the wrong format mask and does not give the required output format. The 'FMDAY' format mask is not correct to get the desired output format.

Option B: This option is incorrect because it uses the wrong format mask and does not give the required output format. The 'FMDD' format mask is not correct to get the desired output format.

Option C: This option is correct. It uses the correct format mask and gives the required output format. The 'FMDay' format mask gives the day of the week in the full name format and 'DD Month, YYYY' gives the date in the required format.

Option D: This option is incorrect because it uses the wrong format mask and does not give the required output format. The 'FMDY' format mask is not correct to get the desired output format.

Option E: This option is incorrect because it uses the wrong function and format mask. TO_DATE function is used to convert a string to a date, not to format the date. Additionally, 'DDD' format mask is not required to get the desired output format.

Therefore, the answer is:

The Answer is: C. SELECT TO_CHAR(SYSDATE, 'FMDay, DD Month, YYYY') FROM dual;

Which SELECT statement will the result 'ello world' from the string 'Hello World'?
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  1. SELECT SUBSTR ('Hello',) FROM dual;

  2. SELECT INITCAP (TRIM ('Hello World',1,1) FROM dual;

  3. SELECT LOWER (SUBSTR ('Hello World',1,1) FROM dual

  4. SELECT LOWER (SUBSTR ('Hello World',2,1) FROM dual;

  5. SELECT LOWER (TRIM ('H' FROM 'Hello World')) FROM dual;

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Correct Option: E

SELECT* FROM order; You use this statement to retrieve data from a data table for __________.
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  1. Updating

  2. Viewing

  3. Deleting

  4. Inserting

  5. Truncating

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Correct Option: B,D

Which four statements correctly describe functions that are available in SQL? (Choose four)
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  1. INSTR returns the numeric position of a named character.

  2. NVL2 returns the first non-null expression in the expression list.

  3. DECODE translates an expression after comparing it to each search value

  4. TRIM trims the heading of trailing characters (or both) from a character string

  5. NVL compares two expressions and returns null if they are equal, or the first expression of they are not equal

  6. NULLIF compares twp expressions and returns null if they are equal, or the first expression if they are not equal

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Correct Option: A,C,D,F

Which two tasks can your perform by using the TO_CHAR function? (Choose two)

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  1. Convert 10 to 'TEN'

  2. Convert '10' to 10

  3. Convert '10' to '10'

  4. Convert 'TEN' to 10

  5. Convert a date to a character expression

  6. Convert a character expression to a date

Show answer
Correct Option: C,E

AI Explanation

To answer this question, let's go through each option to understand which tasks can be performed using the TO_CHAR function:

Option A) Convert 10 to 'TEN' - The TO_CHAR function is used to convert a value to a character expression. It is not used to convert a numeric value to a string representation, so this option is incorrect.

Option B) Convert '10' to 10 - The TO_CHAR function is not used to convert a string representation of a number to a numeric value. This option is incorrect.

Option C) Convert '10' to '10' - The TO_CHAR function is used to convert a value to a character expression. In this case, it can be used to convert the string '10' to the string '10'. This option is correct.

Option D) Convert 'TEN' to 10 - The TO_CHAR function is not used to convert a string representation of a number to a numeric value. This option is incorrect.

Option E) Convert a date to a character expression - The TO_CHAR function can be used to convert a date to a character expression. This option is correct.

Option F) Convert a character expression to a date - The TO_CHAR function is used to convert a value to a character expression, not to convert a character expression to a date. This option is incorrect.

The correct answers are: C) Convert '10' to '10', and E) Convert a date to a character expression.

Which two statements are true regarding the ORDER BY clause? (Choose two)
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  1. The sort is in ascending by order by default

  2. The sort is in descending order by default

  3. The ORDER BY clause must precede the WHERE clause

  4. The ORDER BY clause is executed on the client side

  5. The ORDER BY clause comes last in the SELECT statement

  6. The ORDER BY clause is executed first in the query execution

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Correct Option: A,E

The UPDATE SQL clause can…
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  1. update more than one row at a time.

  2. delete more than one row at a time.

  3. update only one row at a time.

  4. delete only one row at a time.

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Correct Option: A

Which are DML statements? (Choose all that apply)
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  1. COMMIT

  2. MERGE

  3. UPDATE

  4. DELETE

  5. CREATE

  6. DROP

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Correct Option: B,C,D

Which of the following SQL clauses specifies a search condition?
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  1. FROM

  2. SEARCH

  3. WHERE

  4. while

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Correct Option: C