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PostgreSQL STRING_AGG() Function Guide
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- Function Overview
- STRING_AGG() concatenates strings with specified delimiter between them
- Function was introduced in PostgreSQL 9.0 (2010)
- Returns results in string type, unlike ARRAY_AGG() which returns arrays
- Syntax and Requirements
- Requires expression and delimiter/separator parameters
- Must be used with GROUP BY clause
- Default delimiter must be specified as second argument
- Key Features
- Supports various delimiter symbols for string concatenation
- Can remove duplicates using DISTINCT keyword
- Allows ordering results using ORDER BY clause
- Works with character string data types
- Practical Applications
- Creates comma-separated values from multiple columns
- Can combine values from different columns
- Useful for aggregating data labels into array format
- Enhances query performance for large data sets