String functions

CONCAT():
- CONCAT() is used to concatenate two or more strings together.
Example:
```
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SELECT CONCAT('Hello', ' ', 'World') AS concatenated_string;
```
Output: Hello World
SUBSTRING():
- SUBSTRING() is used to extract a portion of a string based on a starting position and length.
- SUBSTRING(string_expression, start_position, length)
Example:
```
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SELECT SUBSTRING('MySQL Tutorial', 1, 5) AS substring_result;
```
Output: MySQL
UPPER() and LOWER():
- UPPER() converts a string to uppercase, while LOWER() converts it to lowercase.
Example:
```
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SELECT UPPER('hello') AS upper_case, LOWER('WORLD') AS lower_case;
```
Output: HELLO, world
LENGTH():
- LENGTH() returns the length (number of characters) of a string.
Example:
```
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SELECT LENGTH('MySQL') AS string_length;
```
Output: 5
TRIM():
- TRIM() removes leading and trailing spaces from a string.
Example:
```
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SELECT TRIM('   Hello   ') AS trimmed_string;
```
Output: Hello
REPLACE():
- REPLACE() replaces occurrences of a substring within a string with another substring.
Example:
```
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SELECT REPLACE('Hello, World!', 'World', 'John') AS replaced_string;
```
Output: Hello, John!
LEFT() and RIGHT():
- LEFT() returns a specified number of characters from the left of a string, while RIGHT() does the same from the right.
Example:
```
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SELECT LEFT('MySQL Tutorial', 5) AS left_string, RIGHT('MySQL Tutorial', 7) AS right_string;
```
Output: MySQL, Tutorial
LOCATE():
- LOCATE() finds the position of a substring within a string.
Example:
```
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SELECT LOCATE('world', 'Hello, world!') AS position;
```
Output: 7
CONCAT_WS():
- CONCAT_WS() concatenates strings with a specified separator.
Example:
```
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SELECT CONCAT_WS(', ', 'John', 'Doe') AS full_name;
```
Output: John, Doe
CHAR_LENGTH():
- CHAR_LENGTH() returns the number of characters in a string, considering multi-byte characters.
Example:
```
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SELECT CHAR_LENGTH('Café') AS string_length;
```
Output: 4

These are some of the commonly used string functions in MySQL, and they can be helpful for various string manipulation tasks in your SQL queries.