Selecting with multiple WHERE conditions on same column

sql

join

group-by

having

byNikita Barsukov·Oct 28, 2024

"""Finding Nemo— let's filter rows with multiple conditions on a single field using IN for equal values:

-- 'Nemo', 'Dory', and 'Bruce' walk into a bar
SELECT * FROM your_table WHERE your_column IN ('Nemo', 'Dory', 'Bruce');

Or when you just keep swimming, you can use each condition with OR:

-- Bruce says: "I'm a nice shark, not a mindless eating machine"
SELECT * FROM your_table WHERE your_column > 'Nemo' OR your_column = 'Bruce';

For dealing with complex filters, joins on subqueries can save the day:

-- An anemone home never looked so big!
SELECT * FROM your_table 
JOIN (
  SELECT your_column FROM your_table WHERE your_condition
  ) AS filter 
ON your_table.your_column = filter.your_column;

Just remember to use your_table, your_column, and your_condition fitting your schema's properties. It's a big, blue world out there.

Comprehensive Strategy with GROUP BY and HAVING

Through a journey like Marlin’s, you might need to successfully meet allWHERE conditions. In such cases, GROUP BY combined with HAVING COUNT(DISTINCT column) can be trusty guides:

-- Marlin, Dory, and Crush, they're all here!
SELECT ContactID
FROM Contacts
WHERE Flag IN ('Marlin', 'Dory', 'Crush')
GROUP BY ContactID
HAVING COUNT(DISTINCT Flag) = 3;

This ensures that all our Flag friends are plunged into the party.

Multiple criteria comparison with JOINs

Instead, if our journey happens to mirror Dory's, then a forgetful fish can benefit from self-joining each criterion:

-- P.Sherman, 42 Wallaby Way, Sydney. I remembered it again!
SELECT a.ContactID
FROM Contacts a
JOIN Contacts b ON a.ContactID = b.ContactID AND b.Flag = 'Sydney'
JOIN Contacts c ON a.ContactID = c.ContactID AND c.Flag = 'Wallaby'
WHERE a.Flag = 'Sherman';

In the heart of the ocean, this method can be extremely efficient for shorter lists of criteria and properly indexed databases. Fish are friends, not food—so test both GROUP BY/HAVING and JOINs on your dataset for the best friendship.

Commonality through INTERSECT

When we're in the jellies, the INTERSECT operator efficiently lets us find common ContactIDs across multiple criteria:

-- Alright, we're here, Peach! 
-- The dentist's niece, Darla, is a repeat offender.
SELECT ContactID FROM Contacts WHERE Flag = 'Peach'
INTERSECT
SELECT ContactID FROM Contacts WHERE Flag = 'Darla';

This operation can un-sting the complexity and streamline INTERSECT operations in our database.

Efficiency in the Current

When riding the East Australian Current, remember these factors:

List Length: The shorter the list (or queue of turtles) for IN or OR, the faster they’ll ride the EAC.
Unique Matches: Use GROUP BY and HAVING to ensure all sea turtles make it.
Subqueries: They simplify complex reef navigation.

Potential Bait

Dive deep but keep out for sharks:

Data Types: Ensure you're dealing with fish, not sharks or birds.
Duplicates: Too many Dories can blur the situation—go for COUNT(DISTINCT ...).
Partial Matches: Use LIKE to find friends who sort of remember the address.

Precision

Every journey requires a well-plotted course. No matter how big or small your quest is, factors like IN, GROUP BY, JOIN, and INTERSECT can help you navigate through your data fleet. Just keep swimming. You’ll sort your WHERE conditions in no time!

explain-codes / Sql / Selecting with multiple WHERE conditions on same column

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