Mysql, Concatenate two columns

sql

join

concatenation

data-integrity

byAlex Kataev·Dec 18, 2024

Simultaneously merge two MySQL fields using the CONCAT() function:

SELECT CONCAT(column1, ' ', column2) AS combined_column FROM table_name;

In this example, column1 and column2 are combined with a space in between, spawning a new combined_column for each record. To include a distinct separator, opt for CONCAT_WS() which includes the separator between non-null strings:

SELECT CONCAT_WS(' - ', column1, column2) AS combined_column FROM table_name;

When concocting unique identifiers, a counter with LPAD() function pads numbers with leading zeros, adding a unique spice to each entry:

SELECT CONCAT(column1, LPAD(column2, 4, '0')) AS unique_id FROM table_name;

For data type conversion when merging different types, CAST() is your magic wand:

SELECT CONCAT(column1, CAST(column2 AS CHAR)) AS combined_column FROM table_name;

Don't forget to gift an alias in your SELECT statement for streamlined future reference.

Fast-track unique data generation

Concatenate seamlessly: CONCAT()

Embrace CONCAT(), an adept artisan, for a harmonious fusion of data.

Data type conversion: CAST()

CAST() ensures your data types get along like old pals, paving way for a smooth concatenation.

Unique identifiers: COUNTERS and LPAD()

Deploy a counter with LPAD() for uniqueness that stands apart in a data crowd.

Use aliases

Your concatenated column deserves an identity- a friendly, recognizable alias.

Practical use cases and solutions

Various concatenation scenarios require careful crafting. You need to ensure, above all, the data integrity.

Averting NULL chaos

NULL values: the wild spirits of your dataset. Keep them from wreaking havoc on your perfectly crafted strings:

SELECT CONCAT_WS('-', column1, column2) AS safe_concat FROM table_name;

CONCAT_WS() bypasses the NULL values, assuring string safety.

Choosing the right separator

A well-chosen separator is like a pause in a song, enhancing the readability rhythm:

SELECT CONCAT(column1, '|', column2) AS readable_concat FROM table_name;

Choose a separator that complements your dataset’s melody while maintaining its meaning.

Combining from multiple tables: JOIN with CONCAT()

As you venture into multi-table concatenation, allow INNER JOIN to be your companion:

SELECT CONCAT(a.column1, ' ', b.column2) AS combined_column
FROM table_a AS a 
INNER JOIN table_b AS b 
ON a.id = b.foreign_id;

PHP-side concatenation

In PHP, concatenate your SQL-fetched data using "." symbol and assign it to a variable for stellar results:

$combinedValue = $row['column1'] . " " . $row['column2']; // PHP's CONCAT is just '.'

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