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.

Show answer
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;

Show answer
Correct Option: E

AI Explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) SELECT SUBSTR ('Hello',) FROM dual; This option is incorrect because the SUBSTR function requires three arguments: the string, the starting position, and the length. In this case, the starting position and length are not provided.

Option B) SELECT INITCAP (TRIM ('Hello World',1,1) FROM dual; This option is incorrect because the TRIM function is used to remove specified characters from the beginning and/or end of a string. In this case, the starting position and length are not provided correctly.

Option C) SELECT LOWER (SUBSTR ('Hello World',1,1) FROM dual This option is incorrect because the SUBSTR function is used to extract a substring from a string. In this case, it is extracting the first character 'H' and converting it to lowercase using the LOWER function. It does not provide the desired result 'ello world'.

Option D) SELECT LOWER (SUBSTR ('Hello World',2,1) FROM dual; This option is incorrect because the SUBSTR function is used to extract a substring from a string. In this case, it is extracting the second character 'e' and converting it to lowercase using the LOWER function. It does not provide the desired result 'ello world'.

Option E) SELECT LOWER (TRIM ('H' FROM 'Hello World')) FROM dual; This option is correct because it uses the TRIM function to remove the letter 'H' from the string 'Hello World'. It then converts the remaining string 'ello world' to lowercase using the LOWER function. This provides the desired result 'ello world'.

The correct answer is 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

Show answer
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

Show answer
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

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

Show answer
Correct Option: A,E

AI Explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) The sort is in ascending order by default - This option is correct. If the ORDER BY clause does not specify ASC or DESC, the sort order is ascending by default.

Option B) The sort is in descending order by default - This option is incorrect. As mentioned above, the sort order is ascending by default.

Option C) The ORDER BY clause must precede the WHERE clause - This option is incorrect. The WHERE clause is used to filter rows based on a condition, and it comes before the ORDER BY clause in the SELECT statement.

Option D) The ORDER BY clause is executed on the client side - This option is incorrect. The ORDER BY clause is executed on the database server side, not on the client side.

Option E) The ORDER BY clause comes last in the SELECT statement - This option is correct. The ORDER BY clause is typically the last clause in a SELECT statement, used to sort the result set based on one or more columns.

Option F) The ORDER BY clause is executed first in the query execution - This option is incorrect. The ORDER BY clause is executed after the WHERE clause and other clauses (such as GROUP BY and HAVING) that may be present in the query.

The correct answers are A and E. The sort is in ascending order by default, and the ORDER BY clause comes last in the SELECT statement.

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.

Show answer
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

Show answer
Correct Option: B,C,D

AI Explanation

To answer this question, we need to understand what DML (Data Manipulation Language) statements are. DML statements are used to modify and manipulate data within a database.

Let's go through each option to determine if it is a DML statement:

Option A) COMMIT - This statement is not a DML statement. COMMIT is used to permanently save any changes made within a transaction.

Option B) MERGE - This statement is a DML statement. MERGE is used to combine data from two tables based on a specified condition.

Option C) UPDATE - This statement is a DML statement. UPDATE is used to modify existing data in a table.

Option D) DELETE - This statement is a DML statement. DELETE is used to remove data from a table.

Option E) CREATE - This statement is not a DML statement. CREATE is used to create new database objects, such as tables, indexes, or views.

Option F) DROP - This statement is not a DML statement. DROP is used to remove existing database objects.

Therefore, the correct answers are options B, C, and D.

Which of the following SQL clauses specifies a search condition?

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  1. FROM

  2. SEARCH

  3. WHERE

  4. while

Show answer
Correct Option: C

AI Explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) FROM - This option is incorrect because the FROM clause is used to specify the table or tables from which data will be retrieved.

Option B) SEARCH - This option is incorrect because there is no such SQL clause called SEARCH.

Option C) WHERE - This option is correct because the WHERE clause is used to specify a search condition to filter the rows returned by a SELECT statement.

Option D) WHILE - This option is incorrect because the WHILE clause is not used for specifying a search condition in SQL. It is typically used in programming languages like SQL Server's T-SQL to implement loops.

The correct answer is C) WHERE. This option is correct because the WHERE clause is used to specify a search condition in SQL.