Inserting and querying data in Supabase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the basic method to add new data into a Supabase table?

You use the insert() method on a Supabase client table reference to add new rows of data.

beginner

How do you retrieve all rows from a Supabase table?

Use the select('*') method on the table reference to get all rows and columns.

beginner

What does the eq() filter do in a Supabase query?

It filters rows where a column's value is exactly equal to the given value.

intermediate

Why is it important to handle errors when inserting or querying data in Supabase?

Because network issues or invalid data can cause failures, handling errors helps keep your app stable and informs users properly.

beginner

What is the typical structure of a Supabase insert operation in JavaScript?

You call supabase.from('table').insert([{column1: value1, column2: value2}]) and then handle the returned data or error.

Which Supabase method is used to add new rows to a table?

A select()

B update()

C insert()

D delete()

The insert() method adds new data rows to a table.

How do you get all columns and rows from a Supabase table?

A select('*')

B getAll()

C fetch()

D list()

Using select('*') fetches all columns and rows.

What does eq('id', 5) do in a Supabase query?

A Filters rows where id equals 5

B Filters rows where id is not 5

C Updates id to 5

D Deletes rows with id 5

eq() filters rows matching the exact value.

What should you do after calling insert() in Supabase?

A Immediately reload the page

B Check for errors and handle the response data

C Call <code>select()</code> automatically

D Nothing, it always succeeds

Always check for errors and handle the response to keep your app stable.

Which of these is a valid way to insert data into a Supabase table named 'users'?

A supabase.create('users', {name: 'Anna'})

B supabase.insert('users', {name: 'Anna'})

C supabase.add('users', 'Anna')

D supabase.from('users').insert([{name: 'Anna'}])

The correct syntax uses from('table').insert([{...}]).

Explain how to insert a new row into a Supabase table and handle the response.

Think about the method chain and error checking.

Describe how to query all data from a Supabase table and filter results by a column value.

Focus on select and filter methods.

Practice

1. What does the insert() method do in Supabase?

easy

A. Adds new rows of data to a table

B. Deletes rows from a table

C. Updates existing rows in a table

D. Retrieves data from a table

Solution

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

   The insert() method is used to add new data entries (rows) into a database table.

2. Step 2: Differentiate from other methods

   Methods like delete() remove data, update() changes existing data, and select() retrieves data. Only insert() adds new rows.

3. Final Answer:

   Adds new rows of data to a table -> Option A

4. Quick Check:

   insert() = Add rows [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 insert a new user with name 'Alice' into the 'users' table using Supabase client?

easy

A. supabase.insert('users').from({name: 'Alice'})

B. supabase.users.insert('Alice')

C. supabase.table('users').add({name: 'Alice'})

D. supabase.from('users').insert({name: 'Alice'})

Solution

1. Step 1: Recall Supabase insert syntax

   The correct syntax uses supabase.from('table').insert(data) to add data.

2. Step 2: Match syntax with options

   supabase.from('users').insert({name: 'Alice'}) matches the correct pattern: supabase.from('users').insert({name: 'Alice'}). Others misuse method order or names.

3. Final Answer:

   supabase.from('users').insert({name: 'Alice'}) -> Option D

4. Quick Check:

   from('table').insert(data) = correct syntax [OK]

Hint: Use from('table').insert({data}) to add rows [OK]

Common Mistakes:

• Swapping method order like insert().from()
• Using non-existent methods like add()
• Passing data as string instead of object

3. Given this code snippet, what will be the output?

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

medium

A. An empty array always

B. An error message because of wrong syntax

C. An array of products where category is 'books'

D. All products regardless of category

Solution

1. Step 1: Understand the query filters

   The select('*') fetches all columns, and .eq('category', 'books') filters rows where category equals 'books'.

2. Step 2: Predict the output of console.log(data)

   It will print an array of product objects matching the category 'books'. If no error, data contains matching rows.

3. Final Answer:

   An array of products where category is 'books' -> Option C

4. Quick Check:

   select('*').eq() filters rows = filtered array [OK]

Hint: eq() filters rows by column value [OK]

Common Mistakes:

• Thinking select('*') returns all rows without filter
• Assuming syntax error due to chaining
• Expecting empty array without data

4. What is wrong with this Supabase insert code?

const { data, error } = await supabase
  .from('orders')
  .insert(['item', 'quantity']);

medium

A. insert() expects an array of objects, not an array of strings

B. from() should be called after insert()

C. insert() cannot be awaited

D. Missing .select() after insert()

Solution

1. Step 1: Check insert() argument type

   The insert() method requires an array of objects representing rows, e.g., [{item: 'apple', quantity: 2}]. Passing an array of strings is invalid.

2. Step 2: Verify method order and usage

   Calling from() before insert() is correct. Awaiting insert() is valid. .select() after insert() is optional for returning data.

3. Final Answer:

   insert() expects an array of objects, not an array of strings -> Option A

4. Quick Check:

   insert() needs array of objects [OK]

Hint: Insert data as objects inside array [OK]

Common Mistakes:

• Passing array of strings instead of objects
• Calling from() after insert()
• Thinking insert() can't be awaited

5. You want to insert multiple new users and then immediately fetch all users with age over 20. Which code correctly does this in Supabase?

hard

A. const { data } = await supabase.from('users').select('*').gt('age', 20);
await supabase.from('users').insert([{name: 'Bob', age: 25}, {name: 'Eve', age: 22}]);

B. await supabase.from('users').insert([{name: 'Bob', age: 25}, {name: 'Eve', age: 22}]);
const { data } = await supabase.from('users').select('*').gt('age', 20);

C. await supabase.from('users').insert({name: 'Bob', age: 25, name: 'Eve', age: 22});
const { data } = await supabase.from('users').select('*').gt('age', 20);

D. await supabase.from('users').insert([{name: 'Bob', age: 25}, {name: 'Eve', age: 22}]).select('*').gt('age', 20);

Solution

1. Step 1: Insert multiple users correctly

   Use insert() with an array of objects: [{name: 'Bob', age: 25}, {name: 'Eve', age: 22}]. A single malformed object is invalid.

2. Step 2: Query users with age > 20 after insertion

   Insert first, then use a separate query: supabase.from('users').select('*').gt('age', 20). Querying before insert misses new data; chaining select().gt() after insert() is invalid.

3. Final Answer:

   Insert first, then query with .gt('age', 20) -> Option B

4. Quick Check:

   Insert then query = correct order [OK]

Hint: Insert first, then query filtered data [OK]

Common Mistakes:

• Querying before inserting new data
• Passing single object instead of array for multiple inserts
• Chaining select() after insert() incorrectly