TOP vs LIMIT across databases in SQL - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select the first 5 rows using SQL Server syntax.

SQL

SELECT [1] 5 * FROM Employees;

Drag options to blanks, or click blank then click option'

ALIMIT

BROWNUM

CTOP

DFETCH

Attempts:

3 left

💡 Hint

Common Mistakes

Using LIMIT which is for MySQL/PostgreSQL.

Using FETCH which is part of OFFSET-FETCH syntax.

In SQL Server, TOP is used to limit the number of rows returned.

2fill in blank

medium

Complete the code to select the first 10 rows using MySQL syntax.

SQL

SELECT * FROM Customers [1] 10;

Drag options to blanks, or click blank then click option'

ALIMIT

BTOP

CFETCH

DROWNUM

Attempts:

3 left

💡 Hint

Common Mistakes

Using TOP which is not valid in MySQL.

Placing LIMIT before FROM clause.

In MySQL, LIMIT is used at the end of the query to restrict rows.

3fill in blank

hard

Fix the error in this PostgreSQL query to limit results to 3 rows.

SQL

SELECT * FROM Orders [1] 3;

Drag options to blanks, or click blank then click option'

ALIMIT

BTOP

CFETCH FIRST

DROWNUM

Attempts:

3 left

💡 Hint

Common Mistakes

Using TOP which is for SQL Server.

Using FETCH FIRST without OFFSET.

PostgreSQL uses LIMIT at the end to restrict rows returned.

4fill in blank

hard

Fill both blanks to select the first 7 rows in Oracle 12c or later.

SQL

SELECT * FROM Products [1] [2] 7 ROWS ONLY;

Drag options to blanks, or click blank then click option'

AFETCH

BLIMIT

CFIRST

DTOP

Attempts:

3 left

💡 Hint

Common Mistakes

Using LIMIT which is not supported in Oracle.

Using TOP which is for SQL Server.

Oracle 12c+ uses FETCH FIRST n ROWS ONLY to limit rows.

5fill in blank

hard

Fill all three blanks to select the first 4 rows in Oracle 12c+ with full syntax.

SQL

SELECT * FROM Sales ORDER BY SaleDate [1] [2] 4 [3];

Drag options to blanks, or click blank then click option'

AFETCH

BFIRST

CROWS ONLY

DLIMIT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LIMIT which is not valid in Oracle.

Omitting ROWS ONLY at the end.

Oracle 12c+ uses FETCH FIRST n ROWS ONLY after ORDER BY to limit rows.

Practice

1. Which SQL clause is used to limit the number of rows returned in SQL Server?

easy

A. LIMIT

B. TOP

C. FETCH FIRST

D. ROWNUM

Solution

1. Step 1: Understand SQL Server syntax

   SQL Server uses the TOP clause immediately after SELECT to limit rows.

2. Step 2: Compare with other databases

   Other databases like MySQL and PostgreSQL use LIMIT at the end, not SQL Server.

3. Final Answer:

   TOP -> Option B

4. Quick Check:

   SQL Server = TOP [OK]

Hint: Use TOP right after SELECT in SQL Server [OK]

Common Mistakes:

• Using LIMIT in SQL Server
• Placing TOP at the end of the query
• Confusing FETCH FIRST with TOP

2. Which of the following is the correct syntax to get the first 5 rows in MySQL?

easy

A. SELECT * FROM table_name LIMIT 5;

B. SELECT TOP 5 * FROM table_name;

C. SELECT * FROM table_name FETCH FIRST 5 ROWS;

D. SELECT * FROM table_name WHERE ROWNUM <= 5;

Solution

1. Step 1: Recall MySQL syntax for limiting rows

   MySQL uses LIMIT at the end of the query to restrict rows.

2. Step 2: Check each option

   SELECT * FROM table_name LIMIT 5; uses LIMIT 5 correctly; SELECT TOP 5 * FROM table_name; uses SQL Server syntax; Options C and D are for other databases.

3. Final Answer:

   SELECT * FROM table_name LIMIT 5; -> Option A

4. Quick Check:

   MySQL = LIMIT at end [OK]

Hint: Use LIMIT at the end in MySQL queries [OK]

Common Mistakes:

• Using TOP in MySQL
• Placing LIMIT before FROM
• Using ROWNUM which is Oracle syntax

3. Given the table Employees with columns Id and Name, what will this query return in SQL Server?

SELECT TOP 3 Name FROM Employees ORDER BY Id DESC;

medium

A. The first 3 employees ordered by Id ascending

B. The last 3 employees ordered by Id descending

C. Syntax error due to TOP placement

D. The top 3 employees ordered by Id descending

Solution

1. Step 1: Understand TOP with ORDER BY in SQL Server

   The query selects the top 3 rows after ordering by Id descending, so highest Ids first.

2. Step 2: Analyze the result

   The result is the 3 employees with the highest Id values, ordered descending.

3. Final Answer:

   The top 3 employees ordered by Id descending -> Option D

4. Quick Check:

   TOP 3 + ORDER BY DESC = highest 3 rows [OK]

Hint: TOP limits rows after ORDER BY sorting [OK]

Common Mistakes:

• Thinking TOP returns first rows before ORDER BY
• Confusing ascending and descending order
• Assuming syntax error with TOP

4. Identify the error in this PostgreSQL query:

SELECT TOP 10 * FROM Customers;

medium

A. TOP is not valid in PostgreSQL

B. Missing ORDER BY clause

C. LIMIT should be placed before FROM

D. Syntax is correct

Solution

1. Step 1: Recall PostgreSQL syntax for limiting rows

   PostgreSQL uses LIMIT at the end, not TOP.

2. Step 2: Check the query

   The query uses TOP 10, which is invalid syntax in PostgreSQL and causes an error.

3. Final Answer:

   TOP is not valid in PostgreSQL -> Option A

4. Quick Check:

   PostgreSQL = LIMIT, not TOP [OK]

Hint: PostgreSQL uses LIMIT, not TOP [OK]

Common Mistakes:

• Using TOP in PostgreSQL
• Placing LIMIT before FROM
• Assuming ORDER BY is mandatory for LIMIT

5. You want to write a query that returns the top 5 highest salaries from an Employees table. Which query works correctly in both SQL Server and MySQL?

hard

A. Use UNION of SQL Server and MySQL queries

B. SELECT Salary FROM Employees ORDER BY Salary DESC LIMIT 5;

C. SELECT Salary FROM Employees ORDER BY Salary DESC FETCH FIRST 5 ROWS ONLY;

D. SELECT TOP 5 Salary FROM Employees ORDER BY Salary DESC;

Solution

1. Step 1: Understand syntax differences

   SQL Server uses TOP after SELECT; MySQL uses LIMIT at the end.

2. Step 2: Check each option for cross-DB compatibility

   SELECT TOP 5 Salary FROM Employees ORDER BY Salary DESC; works only in SQL Server; SELECT Salary FROM Employees ORDER BY Salary DESC LIMIT 5; only in MySQL; Use UNION of SQL Server and MySQL queries doesn't provide a single query that parses in both; SELECT Salary FROM Employees ORDER BY Salary DESC FETCH FIRST 5 ROWS ONLY; is standard SQL supported by both.

3. Final Answer:

   SELECT Salary FROM Employees ORDER BY Salary DESC FETCH FIRST 5 ROWS ONLY; -> Option C

4. Quick Check:

   FETCH FIRST = cross-DB standard [OK]

Hint: Use FETCH FIRST ROWS ONLY for cross-DB compatibility [OK]

Common Mistakes:

• Using LIMIT (MySQL only)
• Using TOP (SQL Server only)
• Proposing UNION which fails parsing