ruby rails where not in
To perform a "where not in" query in Ruby on Rails, you can use the .where.not
method. Here are the steps to perform this query:
- Start by writing the base query using the model you want to query. For example, if you have a
User
model, you can start with:
ruby
User.where.not(...)
- Inside the
.where.not
method, you need to specify the condition for the "not in" query. This condition typically involves a column name and an array of values that you want to exclude. For example, if you want to find users whose IDs are not in the array[1, 2, 3]
, you can write:
ruby
User.where.not(id: [1, 2, 3])
This will generate a SQL query that looks like:
sql
SELECT * FROM users WHERE (users.id NOT IN (1, 2, 3))
The NOT IN
operator is used to exclude the specified values from the query results.
- You can add more conditions to the query by chaining additional
.where.not
or.where
methods. For example, if you want to also exclude users whose names are not in the array['John', 'Jane']
, you can write:
ruby
User.where.not(id: [1, 2, 3]).where.not(name: ['John', 'Jane'])
This will generate a SQL query that looks like:
sql
SELECT * FROM users WHERE (users.id NOT IN (1, 2, 3)) AND (users.name NOT IN ('John', 'Jane'))
The AND
operator is used to combine multiple conditions.
- Finally, you can execute the query and retrieve the results. You can use methods like
.first
to retrieve the first matching record or.all
to retrieve all matching records. For example:
ruby
users = User.where.not(id: [1, 2, 3]).where.not(name: ['John', 'Jane']).all
This will execute the SQL query and return an array of User
objects that match the conditions.
That's it! You have now performed a "where not in" query in Ruby on Rails using the .where.not
method.