[Concept Entry] SIMILAR TO in SQL

content/sql/concepts/operators/terms/similar-to/similar-to.md

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+---
+Title: 'SIMILAR TO'
+Description: 'Used to compare a string to a regular expression'
+Subjects:
+  - 'Data Science'
+  - 'Computer Science'
+Tags:
+  - 'Operators'
+  - 'Database'
+  - 'Queries'
+  - 'PostgreSQL'
+CatalogContent:
+  - 'learn-sql'
+  - 'paths/analyze-data-with-sql'
+---
+
+The **`SIMILAR TO`** operator is primarily found in `PostgreSQL`. It returns `TRUE` if its pattern matches the given string; otherwise, it returns `FALSE`. This operator is similar to the `LIKE` operator used in other databases, such as SQL Server, MySQL, and Oracle SQL, and supports pattern matching via the use of [wildcards](https://www.codecademy.com/resources/docs/sql/wildcards).
+
+## Syntax
+
+`SIMILAR TO` is typically used conditionally with a `WHERE` clause to select rows based on a column matching a given string pattern.
+
+```pseudo
+SELECT *
+FROM table_name
+WHERE column_name SIMILAR TO pattern;
+```
+
+The `pattern` here constitutes a string that includes the following wildcards:
+
+- `%`: Matches zero or more arbitrary characters.
+- `_`: Matches exactly one arbitrary character.
+
+## Example 1
+
+The following example selects every country from the `countries` table where the name starts with "M":
+
+```sql
+SELECT *
+FROM countries
+WHERE country_name SIMILAR TO 'M%';
+```
+
+Explanation:
+
+- `M`: The name must start with the letter "M".
+- `%`: Matches zero or more characters after "M".
+
+Example Matches:
+
+- Mexico
+- Malaysia
+
+## Example 2
+
+The following example selects every `employee` from the `employees` table whose name starts with either `John` or `Jane`:
+
+```sql
+SELECT *
+FROM employees
+WHERE name SIMILAR TO '(John|Jane)%';
+```
+
+Explanation:
+
+- `(John|Jane)`: The name must start with either "John" or "Jane".
+- `%`: Matches zero or more characters after "John" or "Jane".
+
+Example Matches:
+
+- Johnathan
+- John Smith
+
+## Example 3
+
+The following example selects `employees` whose name is either `John` or `Jane`, followed by a middle initial and a period:
+
+```sql
+SELECT *
+FROM employees
+WHERE name SIMILAR TO '(John|Jane)_[A-Z].%';
+```
+
+Explanation:
+
+- `(John|Jane)`: The name must start with either "John" or "Jane".
+- `_`: Matches exactly one arbitrary character (in this case, a space or any other single character).
+- `[A-Z]`: Matches a single uppercase letter, representing a middle initial.
+- `.`: Matches a literal period (used after the middle initial).
+- `%`: Matches zero or more characters after the period, such as a last name or other additional characters.
+
+Example Matches:
+
+- John A. Smith
+- Jane B. Doe