SQL study notes - REGEXP operator

REGEXP operator, short for regular expression (regular expression), regular expression is very powerful when searching for strings, the following is about its application

1. Find customers whose name contains field

select *from customerswhere last_name like '%field%'

Using the REGEXP operator, it can be written like this, and the data can also be obtained

select *from customerswhere last_name regexp 'field'

2. Find customers whose last name starts with Brush

^ indicates what the search string must start with

select *from customerswhere last_name regexp '^brush'

3. Find customers whose last name ends with field

$ indicates what the search string must end with

select *from customerswhere last_name regexp 'field$'

3. Find customers whose last name contains field or mac

|The symbol indicates multiple search patterns

select *from customerswhere last_name regexp 'brush|mac'

4. Find customers that start with brush, or contain mac, or contain rose

select *from customerswhere last_name regexp '^brush|mac|rose'

5. Find the last name contains e, and it must be preceded by g or i or m

select *from customerswhere last_name regexp '[gim]e'

6. Find the last name contains e, followed by a but a letter in h

select *from customerswhere last_name regexp 'e[a-h]'

Summary:

^ means start of string

$ indicates the end of string

|Represents a logical or, which can give multiple search patterns

[] means any single character listed in parentheses

[-] means any single character within brackets

Exercise

1. Get customers whose name is Elka or Ambur

select *from customerswhere first_name regexp 'elka|ambur'

2. Return customers whose last name ends with ey or on

select *from customerswhere last_name regexp 'ey$|on$'

3. Get customers whose last name starts with my or contains se

select *from customerswhere last_name regexp '^my|se'

4. Return the customer, the last name contains b, then r or u

select *from customerswhere last_name regexp 'b[ru]'

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