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And & Or - (PostgreSQL Conditions)

In PostgreSQL, you can use the AND and OR operators to specify multiple conditions in a WHERE clause. In this tutorial, we'll discuss the usage of AND and OR operators in PostgreSQL, explain their difference and show some examples to better understand their usage.

Syntax

The syntax for using the AND and OR operators in PostgreSQL is as follows:

SELECT column_name(s)
FROM table_name
WHERE condition1
AND/OR condition2;
  • column_name(s): The column(s) you want to retrieve data from.
  • table_name: The name of the table you want to retrieve data from.
  • condition1, condition2: The conditions you want to apply to filter the data.

Example

Let's say we have a students table with the following data:

id name age gender
1 Alice 22 F
2 Bob 25 M
3 Claire 19 F
4 David 28 M

We can use the AND and OR operators to select data based on multiple conditions. For example:

-- Select all students who are female AND under 25 years old
SELECT * FROM students WHERE gender = 'F' AND age < 25;

| id | name   | age | gender |
|----|--------|-----|--------|
| 1  | Alice  | 22  | F      |
| 3  | Claire | 19  | F      |

-- Select all students who are male OR over 25 years old
SELECT * FROM students WHERE gender = 'M' OR age >= 25;

| id | name  | age | gender |
|----|-------|-----|--------|
| 2  | Bob   | 25  | M      |
| 4  | David | 28  | M      |

Explanation

In the above examples, we use AND and OR operators to apply multiple conditions to filter the data we want to select. When we use the AND operator, all the conditions must be true for the row to be included in the result. When we use the OR operator, at least one of the conditions must be true for the row to be included in the result.

Use

The AND and OR operators in PostgreSQL are useful when you want to select data based on multiple conditions. By combining multiple conditions, you can narrow down the data you want to select and retrieve only the data that matches your criteria.

Important Points

  • Use parentheses to group conditions when using both AND and OR operators in the same WHERE clause. It's important to use parentheses to ensure that the conditions are evaluated in the correct order.
  • When using multiple operators in a single WHERE clause, the AND operator is evaluated before the OR operator.
  • When you have more than two conditions, you need to chain the AND and OR operators together t form a logical expression.

Summary

In this tutorial, we discussed the usage of AND and OR operators in PostgreSQL and showed some examples to illustrate how they function. We explained the difference between the AND and OR operators, their usage, and their important points to keep in mind. By using AND and OR operators in conjunction with conditions and logical expressions, you can more effectively select data from your PostgreSQL database.

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