MySQL
Expresiones regulares

Introducción

REGEXP / RLIKE

El operador REGEXP (o su sinónimo, RLIKE ) permite la coincidencia de patrones en base a expresiones regulares.

Considere la siguiente tabla de employee :

+-------------+-------------+-------------+--------------+----------+
| EMPLOYEE_ID | FIRST_NAME  | LAST_NAME   | PHONE_NUMBER | SALARY   |
+-------------+-------------+-------------+--------------+----------+
|         100 | Steven      | King        | 515.123.4567 | 24000.00 |
|         101 | Neena       | Kochhar     | 515.123.4568 | 17000.00 |
|         102 | Lex         | De Haan     | 515.123.4569 | 17000.00 |
|         103 | Alexander   | Hunold      | 590.423.4567 |  9000.00 |
|         104 | Bruce       | Ernst       | 590.423.4568 |  6000.00 |
|         105 | David       | Austin      | 590.423.4569 |  4800.00 |
|         106 | Valli       | Pataballa   | 590.423.4560 |  4800.00 |
|         107 | Diana       | Lorentz     | 590.423.5567 |  4200.00 |
|         108 | Nancy       | Greenberg   | 515.124.4569 | 12000.00 |
|         109 | Daniel      | Faviet      | 515.124.4169 |  9000.00 |
|         110 | John        | Chen        | 515.124.4269 |  8200.00 |
+-------------+-------------+-------------+--------------+----------+

Patrón ^

Seleccione todos los empleados cuyo FIRST_NAME comience con N.

Consulta

SELECT * FROM employees WHERE FIRST_NAME REGEXP '^N'
-- Pattern start with----------------------------^

Patrón $ **

Seleccione todos los empleados cuyo PHONE_NUMBER finalice con 4569 .

Consulta

SELECT * FROM employees WHERE PHONE_NUMBER REGEXP '4569$'
-- Pattern end with----------------------------------^

NO REGEXP

Seleccione todos los empleados cuyo FIRST_NAME no comience con N.

Consulta

SELECT * FROM employees WHERE FIRST_NAME NOT REGEXP '^N'
-- Pattern does not start with---------------^

Regex contener

Seleccionar todos los empleados cuyos LAST_NAME contiene y cuya FIRST_NAME contiene a .

Consulta

SELECT * FROM employees WHERE FIRST_NAME REGEXP 'a' AND LAST_NAME REGEXP 'in'
-- No ^ or $, pattern can be anywhere -------------------------------------^

Cualquier caracter entre []

Seleccione todos los empleados cuyo FIRST_NAME comience con A o B o C.

Consulta

SELECT * FROM employees WHERE FIRST_NAME REGEXP '^[ABC]'
-------------------------------------------------^^---^

Patrón o |

Seleccione todos los empleados cuyo FIRST_NAME comience con A o B o C y termine con r , e , o i .

Consulta

SELECT * FROM employees WHERE FIRST_NAME REGEXP '^[ABC]|[rei]$'
-- ----------------------------------------------^^---^^^---^^

Contando coincidencias de expresiones regulares

Considere la siguiente consulta:

SELECT FIRST_NAME, FIRST_NAME REGEXP '^N' as matching FROM employees

FIRST_NAME REGEXP '^N' es 1 o 0 según el hecho de que FIRST_NAME coincida con ^N

Para visualizarlo mejor:

SELECT 
FIRST_NAME, 
IF(FIRST_NAME REGEXP '^N', 'matches ^N', 'does not match ^N') as matching 
FROM employees

Finalmente, cuente el número total de filas coincidentes y no coincidentes con:

SELECT
IF(FIRST_NAME REGEXP '^N', 'matches ^N', 'does not match ^N') as matching,
COUNT(*) 
FROM employees 
GROUP BY matching