Filter Records
The WHERE clause is used to filter records.
It is used to extract only those records that fulfill a specified condition.
If we want to return only the records where city is London, we can specify that in the WHERE clause:
Example
SELECT * FROM customers
WHERE
city = 'London';
Text Fields vs. Numeric Fields
PostgreSQL requires quotes around text values.
However, numeric fields should not be enclosed in quotes:
Example
SELECT * FROM customers
WHERE
customer_id = 19;
Note: Quotes around numeric fields will not fail, but it is good practice to always write numeric values without quotes.
Greater than
Use the > operator to return all records where customer_id is greater than 80:
Example
SELECT * FROM customers
WHERE
customer_id > 80;
Note: Quotes around numeric fields will not fail, but it is good practice to always write numeric values without quotes.
