CRUD operations with supabase-js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a new row into the 'users' table.

Supabase

const { data, error } = await supabase.from('users').[1]({ name: 'Alice', age: 30 });

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

Aselect

Bdelete

Cinsert

Dupdate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'select' instead of 'insert' to add data.

Using 'update' when trying to add new rows.

The insert method adds new rows to a table in Supabase.

2fill in blank

medium

Complete the code to select all rows from the 'products' table.

Supabase

const { data, error } = await supabase.from('products').[1]('*');

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

Ainsert

Bdelete

Cupdate

Dselect

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'insert' when trying to read data.

Using 'delete' instead of 'select'.

The select method retrieves rows from a table. Using '*' selects all columns.

3fill in blank

hard

Fix the error in the code to update the 'age' of a user with id 5.

Supabase

const { data, error } = await supabase.from('users').update({ age: 31 }).[1]('id', 5);

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

Awhere

Beq

Cfilter

Dmatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'where' which is not a Supabase-js method.

Using 'filter' which is not valid here.

The eq method filters rows where a column equals a value. Here, it selects the user with id 5.

4fill in blank

hard

Fill both blanks to delete a product with id 10 from the 'products' table.

Supabase

const { data, error } = await supabase.from('products').[1]().[2]('id', 10);

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

Adelete

Beq

Cselect

Dupdate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'select' instead of 'delete' to remove rows.

Using 'update' instead of 'delete'.

The delete method removes rows. The eq method filters rows where 'id' equals 10.

5fill in blank

hard

Fill all three blanks to select users older than 25 from the 'users' table.

Supabase

const { data, error } = await supabase.from('users').[1]('*').[2]('age', '[3]', 25);

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

Aselect

Bfilter

Cgt

Dlt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'lt' instead of 'gt' for age comparison.

Using 'eq' instead of 'gt' for greater than.

select('*') gets all columns. filter('age', 'gt', 25) selects rows where age is greater than 25.

Practice

1. What does the insert() method do in supabase-js when working with a table?

easy

A. Deletes data rows from the table

B. Adds new data rows to the table

C. Updates existing data rows in the table

D. Fetches data rows from the table

Solution

1. Step 1: Understand the purpose of insert()

   The insert() method is used to add new records to a database table.

2. Step 2: Compare with other CRUD methods

   delete() removes data, update() changes data, and select() fetches data. So insert() must add data.

3. Final Answer:

   Adds new data rows to the table -> Option B

4. Quick Check:

   insert() = add data [OK]

Hint: Insert means add new data rows [OK]

Common Mistakes:

• Confusing insert() with update()
• Thinking insert() deletes data
• Mixing insert() with select()

2. Which of the following is the correct syntax to select all rows from a table named users using supabase-js?

easy

A. supabase.from('users').select('*')

B. supabase.select('*').from('users')

C. supabase.from('users').get('*')

D. supabase.query('users').select('*')

Solution

1. Step 1: Recall supabase-js query structure

   The correct method chain starts with from('table') then select() to specify columns.

2. Step 2: Check each option

   supabase.from('users').select('*') matches the correct order and methods. The other options use incorrect method order or invalid methods.

3. Final Answer:

   supabase.from('users').select('*') -> Option A

4. Quick Check:

   from() then select() = correct syntax [OK]

Hint: Use from('table').select('*') to fetch all rows [OK]

Common Mistakes:

• Swapping order of from() and select()
• Using get() instead of select()
• Using query() which is not a supabase-js method

3. What will be the output of this code snippet?

const { data, error } = await supabase.from('products').select('id, name').eq('category', 'books');
console.log(data);

medium

A. An empty array because 'select' needs all fields specified

B. An error because 'eq' is not a valid method

C. All products with all fields regardless of category

D. An array of products with category 'books' showing only id and name fields

Solution

1. Step 1: Understand the query filters and selects

   The select('id, name') picks only those two fields. The eq('category', 'books') filters rows where category equals 'books'.

2. Step 2: Predict the output

   The result data will be an array of objects with only id and name for products in the 'books' category.

3. Final Answer:

   An array of products with category 'books' showing only id and name fields -> Option D

4. Quick Check:

   select + eq filters data correctly [OK]

Hint: eq() filters rows; select() chooses fields [OK]

Common Mistakes:

• Thinking eq() is invalid
• Assuming select() returns all fields
• Expecting error due to method chaining

4. Identify the error in this supabase-js update code:

const { data, error } = await supabase.from('users').update({ age: 30 }).where('id', 5);

medium

A. Missing select() after update()

B. The update method cannot update numeric fields

C. The method where does not exist; should use eq instead

D. The table name 'users' is invalid

Solution

1. Step 1: Check method chaining for update filters

   supabase-js uses eq() to filter rows, not where().

2. Step 2: Confirm other parts

   Updating numeric fields is allowed, select() is optional, and 'users' is a valid table name.

3. Final Answer:

   The method where does not exist; should use eq instead -> Option C

4. Quick Check:

   Use eq() not where() for filtering [OK]

Hint: Use eq() to filter, not where() [OK]

Common Mistakes:

• Using where() instead of eq()
• Thinking update() needs select() always
• Assuming numeric fields can't be updated

5. You want to delete all rows from the orders table where the status is 'cancelled'. Which code snippet correctly performs this action and handles errors?

hard

A. const { error } = await supabase.from('orders').delete().eq('status', 'cancelled'); if (error) console.error(error);

B. const { data } = await supabase.from('orders').remove().eq('status', 'cancelled'); if (data) console.log(data);

C. const { error } = await supabase.from('orders').delete('status', 'cancelled'); if (error) console.error(error);

D. const { error } = await supabase.from('orders').delete().where('status', 'cancelled'); if (error) console.error(error);

Solution

1. Step 1: Identify correct delete syntax with filter

   supabase-js uses delete() followed by eq('column', value) to filter rows to delete.

2. Step 2: Check error handling

   The code checks if error exists and logs it, which is best practice.

3. Final Answer:

   const { error } = await supabase.from('orders').delete().eq('status', 'cancelled'); if (error) console.error(error); -> Option A

4. Quick Check:

   delete() + eq() + error check = correct [OK]

Hint: Use delete().eq() and check error for safe deletion [OK]

Common Mistakes:

• Using remove() instead of delete()
• Using where() instead of eq()
• Not handling errors after delete