Raw expressions in Laravel - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select users with a raw SQL expression.

Laravel

DB::table('users')->select(DB::raw([1]))->get();

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

A"*"

B"users"

C"count(*) as user_count"

D"id"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to wrap the SQL expression in quotes.

Using column names directly without DB::raw.

The DB::raw method allows you to use raw SQL expressions. Here, "count(*) as user_count" counts users.

2fill in blank

medium

Complete the code to order users by a raw SQL expression.

Laravel

DB::table('users')->orderByRaw([1])->get();

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

A"name DESC"

B"created_at DESC"

C"age ASC"

D"email ASC"

Attempts:

3 left

💡 Hint

Common Mistakes

Using orderBy instead of orderByRaw for raw SQL.

Missing quotes around the raw SQL string.

orderByRaw lets you order results using raw SQL. Here, ordering by created_at DESC shows newest users first.

3fill in blank

hard

Fix the error in the raw where clause to filter users by age.

Laravel

DB::table('users')->whereRaw([1])->get();

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

A"age > 18 OR 1=1"

Bage > 18

C"age > '18'"

D"age > 18"

Attempts:

3 left

💡 Hint

Common Mistakes

Writing raw SQL without quotes causes errors.

Adding unsafe SQL like OR 1=1 can cause security issues.

The raw SQL must be a string. "age > 18" is correct. Without quotes, it causes syntax errors.

4fill in blank

hard

Fill both blanks to create a raw select with alias and a where condition.

Laravel

DB::table('orders')->select(DB::raw([1]))->whereRaw([2])->get();

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

A"SUM(price) as total_price"

B"price > 100"

C"status = 'completed'"

D"COUNT(*) as order_count"

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up select and where raw expressions.

Forgetting quotes around raw SQL strings.

The select uses SUM(price) as total_price to sum prices. The where condition filters completed orders with status = 'completed'.

5fill in blank

hard

Fill all three blanks to build a raw expression with a case statement, alias, and order.

Laravel

DB::table('products')->select(DB::raw([1]))->orderByRaw([2])->whereRaw([3])->get();

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

A"CASE WHEN stock > 0 THEN 'In Stock' ELSE 'Out of Stock' END as availability"

B"availability DESC"

C"price < 50"

D"stock > 10"

Attempts:

3 left

💡 Hint

Common Mistakes

Not wrapping CASE statement in quotes.

Using invalid SQL syntax inside raw expressions.

The select uses a CASE statement to label availability. The order sorts by availability descending. The where filters products priced below 50.

Practice

1. What is the primary purpose of using DB::raw() in Laravel queries?

easy

A. To insert raw SQL expressions directly into the query builder

B. To automatically escape all user inputs

C. To convert Eloquent models into arrays

D. To cache query results for faster access

Solution

1. Step 1: Understand the role of DB::raw()

   DB::raw() allows you to write raw SQL expressions inside Laravel's query builder without modification.

2. Step 2: Compare with other options

   Options B, C, and D describe different Laravel features unrelated to raw SQL expressions.

3. Final Answer:

   To insert raw SQL expressions directly into the query builder -> Option A

4. Quick Check:

   DB::raw() = raw SQL insertion [OK]

Hint: DB::raw() means write SQL exactly as is inside queries [OK]

Common Mistakes:

• Thinking DB::raw() escapes inputs automatically
• Confusing DB::raw() with model conversion
• Assuming DB::raw() caches queries

2. Which of the following is the correct syntax to use DB::raw() in a Laravel query builder to select the current date?

easy

A. DB::table('users')->select(DB::raw('CURRENT_DATE'))->get();

B. DB::table('users')->select('CURRENT_DATE')->get();

C. DB::table('users')->selectRaw('CURRENT_DATE')->get();

D. DB::table('users')->selectRaw(DB::raw('CURRENT_DATE'))->get();

Solution

1. Step 1: Identify correct raw expression usage

   DB::raw() wraps the raw SQL string inside select() to insert it as is.

2. Step 2: Analyze other options

   DB::table('users')->select('CURRENT_DATE')->get(); treats 'CURRENT_DATE' as a column name, not raw SQL. DB::table('users')->selectRaw('CURRENT_DATE')->get(); uses selectRaw() correctly but without DB::raw(), which is valid but not the exact syntax asked. DB::table('users')->selectRaw(DB::raw('CURRENT_DATE'))->get(); nests DB::raw() inside selectRaw(), which is incorrect.

3. Final Answer:

   DB::table('users')->select(DB::raw('CURRENT_DATE'))->get(); -> Option A

4. Quick Check:

   Use DB::raw() inside select() for raw SQL [OK]

Hint: Use DB::raw('SQL') inside select() for raw SQL [OK]

Common Mistakes:

• Using select() with string instead of DB::raw()
• Confusing selectRaw() and DB::raw() usage
• Nesting DB::raw() inside selectRaw() incorrectly

3. What will be the output of the following Laravel query?

DB::table('orders')
  ->select('id', DB::raw('price * quantity AS total'))
  ->where('status', 'completed')
  ->get();

medium

A. An empty collection because raw expressions are not supported in where clauses

B. A syntax error because raw expressions cannot have aliases

C. A collection of orders with id and a calculated total price (price * quantity)

D. A collection with only id and price fields, ignoring quantity

Solution

1. Step 1: Understand the select with DB::raw()

   The query selects 'id' and a raw SQL expression calculating 'price * quantity' as 'total'. This is valid and returns those fields.

2. Step 2: Check the where clause and output

   The where clause filters orders with status 'completed'. The output is a collection of matching orders with 'id' and 'total' fields.

3. Final Answer:

   A collection of orders with id and a calculated total price (price * quantity) -> Option C

4. Quick Check:

   DB::raw() with alias returns calculated fields [OK]

Hint: DB::raw() can calculate fields with aliases in select [OK]

Common Mistakes:

• Thinking raw expressions cannot have aliases
• Assuming raw expressions affect where clause support
• Ignoring the calculated field in output

4. Identify the error in this Laravel query using raw expressions:

DB::table('users')
  ->where(DB::raw('LENGTH(name)'), '>', 5)
  ->get();

medium

A. Raw expressions cannot be used inside where clauses

B. The syntax is correct; no error present

C. DB::raw() should be wrapped inside a closure for where

D. The comparison operator '>' is invalid in this context

Solution

1. Step 1: Review usage of DB::raw() in where clause

   Using DB::raw() inside where to apply SQL functions like LENGTH() is valid syntax in Laravel.

2. Step 2: Check operators and syntax

   The '>' operator is valid for comparison. No wrapping closure is required here.

3. Final Answer:

   The syntax is correct; no error present -> Option B

4. Quick Check:

   DB::raw() works in where clauses with operators [OK]

Hint: DB::raw() can be used directly in where with operators [OK]

Common Mistakes:

• Assuming raw expressions are disallowed in where
• Thinking a closure is needed for DB::raw() in where
• Misunderstanding comparison operator validity

5. You want to update all users' scores by adding 10 points using a raw SQL expression in Laravel. Which code snippet correctly achieves this safely?

hard

A. DB::table('users')->update(DB::raw('score = score + 10'));

B. DB::table('users')->update(['score' => 'score + 10']);

C. DB::table('users')->updateRaw('score = score + 10');

D. DB::table('users')->update(['score' => DB::raw('score + 10')]);

Solution

1. Step 1: Understand how to update with raw expressions

   To update a column by adding a value, use DB::raw() inside the update array to write the SQL expression.

2. Step 2: Analyze each option

   DB::table('users')->update(['score' => DB::raw('score + 10')]); correctly uses DB::raw('score + 10') as the new value. DB::table('users')->update(['score' => 'score + 10']); treats it as a string, not SQL. DB::table('users')->update(DB::raw('score = score + 10')); passes DB::raw() directly to update(), which expects an array, causing error. DB::table('users')->updateRaw('score = score + 10'); uses a non-existent updateRaw() method.

3. Final Answer:

   DB::table('users')->update(['score' => DB::raw('score + 10')]); -> Option D

4. Quick Check:

   Use DB::raw() inside update array for calculations [OK]

Hint: Use DB::raw() inside update array for arithmetic updates [OK]

Common Mistakes:

• Passing raw SQL as string without DB::raw()
• Calling non-existent updateRaw() method
• Passing DB::raw() directly instead of in array