MySQL CONCAT() Function

 The CONCAT() function in MySQL is used to concatenate two or more strings into a single string. It combines the values of the strings and returns the result.

Syntax:

CONCAT(string1, string2, ..., stringN)

• string1, string2, ..., stringN: The strings to concatenate. You can pass column names, literals, or expressions.

If any of the arguments is NULL, the CONCAT() function returns NULL. To avoid this, use CONCAT_WS() or handle NULL values explicitly.

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Example Usages:

1. Concatenating String Literals:

SELECT CONCAT('Hello', ' ', 'World') AS Result;
-- Output: "Hello World"

2. Concatenating Columns:

SELECT CONCAT(first_name, ' ', last_name) AS FullName
FROM employees;
-- Output: "John Doe", "Jane Smith", etc.

3. Handling NULL Values:

SELECT CONCAT('Hello', NULL, 'World') AS Result;
-- Output: NULL

4. Using IFNULL() to Avoid NULL Result:

SELECT CONCAT(IFNULL(first_name, ''), ' ', IFNULL(last_name, '')) AS FullName
FROM employees;

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Notes:

• To use a delimiter between concatenated strings, consider using CONCAT_WS(), which includes a separator:

  SELECT CONCAT_WS('-', '2024', '12', '20') AS Date;
  -- Output: "2024-12-20"
  

• CONCAT() can be useful in constructing dynamic SQL queries or formatting output for reports.

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