🧬 Regex for Advanced Filtering

Last Updated: January 2026

Regex allows pattern-based filtering when simple conditions are not enough. It is commonly used with:

REGEXP / RLIKE (MySQL)
~ operator (PostgreSQL)

Hinglish Tip 🗣: Regex tab use hota hai jab filter rule-based pattern par depend karta ho.

Basic Usage

SELECT column_name
FROM table_name
WHERE column_name REGEXP 'pattern';

🔤 Core Regex Symbols

Symbol	Description	Example	Matches
`^`	Matches the start of the string or line	`^Hello`	`Hello there` (start match)
`$`	Matches the end of the string or line	`end$`	`The end` (end match)
`{m}`	Matches exactly `m` repetitions of the preceding element	`a{3}`	`aaa`
`{m,}`	Matches at least `m` repetitions of the preceding element	`a{2,}`	`aa`, `aaa`
`{(m, n)}`	Matches between `m` and `n` repetitions	`a{(2, 4)}`	`aa`, `aaa`, `aaaa`
`( ... )`	Groups patterns or captures matched substring	`(ab)+`	`ab`, `abab`, `ababab`
`\|`	OR operator: matches either pattern on left or right	`cat\|dog`	`cat` or `dog`
`[abc]`	Character class: matches any one character listed	`[aeiou]`	any vowel
`[^abc]`	Negated character class: matches any character not listed	`[^0-9]`	any non-digit character
`\`	Escape character: matches a literal backslash or special char	`\.`	a literal dot `.`
`.`	Matches any single character except newline	`a.b`	`aab`, `acb`, `a9b`
`*`	Matches zero or more repetitions of the previous character	`ca*t`	`ct`, `cat`, `caaaat`
`+`	Matches one or more repetitions of the previous character	`go+gle`	`gogle`, `google`, `gooogle`
`?`	Matches zero or one repetition (makes preceding optional)	`colou?r`	`color`, `colour`
`\b`	Matches a word boundary	`\bcat\b`	`cat` but not `cats` or `cat.`
`\d`	Matches any digit (0-9)	`\d{}`	`123`, `456`, `007`
`\D`	Matches any non-digit character	`\D+`	`abc`, `!@#`
`\w`	Matches any alphanumeric character or underscore	`\w+`	`hello123`, `_var`
`\W`	Matches any non-word character	`\W+`	`!@#`, spaces
`\s`	Matches any whitespace character (space, tab, newline)	`\s+`	space, tab, newline
`\S`	Matches any non-whitespace character	`\S+`	`hello`, `123`

🔍 SQL Examples

^ — Starts With

SELECT name
FROM students
WHERE name REGEXP '^A';

$ — Ends With

SELECT name
FROM students
WHERE name REGEXP 'n$';

| — OR

SELECT name
FROM students
WHERE name REGEXP 'Ram|Shyam';

. — Any One Character

SELECT code
FROM products
WHERE code REGEXP 'A.B';

Matches: A1B, ACB, A-B

* — Zero or More

SELECT value
FROM logs
WHERE value REGEXP 'ab*';

Matches: a, ab, abb

[] — Character Set

SELECT name
FROM students
WHERE name REGEXP '^[A-Z]';

+ — One or More

SELECT name
FROM users
WHERE name REGEXP 'a+';

? — Zero or One

SELECT color
FROM items
WHERE color REGEXP 'colou?r';

Matches: color, colour

{m} — Exact Count

SELECT pin
FROM addresses
WHERE pin REGEXP '^[0-9]{6}$';

{m, or } — Minimum Count

SELECT username
FROM users
WHERE username REGEXP '[a-z]{5,}';

{n, m} — Range Count

SELECT code
FROM products
WHERE code REGEXP '[A-Z]{2,4}';

⚠️ Important Notes

Regex support varies slightly by database
Always test patterns before using in production
Use anchors (^, $) to avoid partial matches

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