How Does MySQL Handle OR and AND Operators in Queries?

MySQL OR/AND Precedence

Understanding operator precedence is crucial when crafting MySQL queries. In the example provided, you wanted to select rows where display = 1 or 2 and where any of the content, tags, or title contains "hello world."

According to MySQL documentation, the precedence of the logical operators is as follows:

• Highest: !, ~
• AND
• OR
• = (comparison), IN, BETWEEN, LIKE, REGEXP
• Lowest: assignment, :=

Therefore, the query you provided would be interpreted as:

(display = 1) OR (
    (display = 2)
    AND (content like "%hello world%")
)
OR (tags like "%hello world%")
OR (title like "%hello world%")

To ensure your intentions are clear, consider using parentheses explicitly, especially when dealing with complex expressions. A more explicit version of the query might look like this:

(
    (display = 1)
    OR (display = 2)
)
AND (
    (content like "%hello world%")
    OR (tags like "%hello world%")
    OR (title like "%hello world%")
)

This makes it unambiguous that the OR and AND operators apply as intended.

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