Features
SQL CONCATENATE joins two or more strings or column values directly inside a query to form one continuous string.
SQL concatenation joins two or more strings or column values into one continuous string directly within a SELECT, UPDATE, or INSERT statement.
SQL CONCATENATE is the act of joining two or more character strings into one string inside a query. Most engines provide the CONCAT() function or the double-pipe (||) operator to perform this operation.
Placing concatenation in SQL reduces network round-trips, lets the database exploit indexes and pushdowns, and keeps logic close to the data — improving performance and maintainability.
ANSI SQL defines the || operator for string concatenation. Example: SELECT 'Dr. ' || first_name || ' ' || last_name AS full_name FROM doctors;
Use CONCAT() when you need portability across MySQL, SQL Server, PostgreSQL, Snowflake, BigQuery, and Redshift. CONCAT(val1, val2) safely casts non-string types and returns NULL only when all inputs are NULL.
The || operator is shorter to type and works in PostgreSQL, Snowflake, Redshift, Oracle, and BigQuery. It fails if any operand is NULL, unless the engine supports NULL-safe concatenation settings.
CONCAT_WS(separator, val1, val2, …) inserts the separator only between non-NULL arguments. Example: SELECT CONCAT_WS('-', year, month, day) AS yyyymmdd FROM dates;
CONCAT() returns NULL only when every argument is NULL. The || operator returns NULL if any operand is NULL. Use COALESCE(val,'') to override NULLs or enable CONCAT_NULL_YIELDS_NULL OFF in SQL Server.
Cast numbers once, avoid concatenating inside predicates, and index computed columns when possible. Precompute large concatenations into materialized views to speed downstream queries.
1. Forgotten NULL handling — wrap columns with COALESCE(). 2. Mixed data types — CAST integers before concatenation. 3. Unexpected spaces — TRIM() source columns.
SELECT order_id,
CONCAT_WS(' | ', customer_name, city, state) AS customer_location,
total_amount
FROM orders
ORDER BY order_id;
Galaxy’s AI copilot autocompletes CONCAT, CONCAT_WS, and || patterns, suggests COALESCE for NULLs, and formats long expressions. Endorse shared queries so teams reuse the correct concatenation logic without Slack copy-paste.
String concatenation is critical for building user-friendly labels, search keys, JSON paths, CSV exports, and dynamic SQL right inside the database. Knowing how to do it safely prevents NULL traps and performance hits.
Yes. Both databases implement CONCAT(), and PostgreSQL also supports the ANSI || operator, giving two options.
Use COALESCE(column,'') to replace NULLs with empty strings or use CONCAT_WS, which skips NULL inputs automatically.
CONCAT simply joins inputs end-to-end. CONCAT_WS adds your chosen separator between non-NULL arguments.
Galaxy's AI copilot autocompletes CONCAT patterns, highlights NULL pitfalls, and makes tested concatenation queries shareable across your team.
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