string_agg() — PostgreSQL aggregate aggregate function

string_agg(): concatenate aggregate input into a string. PostgreSQL aggregate functions — signature, volatility, version applicability and an illustrative example.

The Sev-1 Admin
The Sev-1 Admin  ·  2 min read

Summary

string_agg is a PostgreSQL built-in aggregate function in the Aggregate Functions group. PostgreSQL’s system catalog (pg_proc) describes it as: “concatenate aggregate input into a string”.

Signature

string_agg has 2 documented overloaded forms:

string_agg(text, text) → text
string_agg(bytea, bytea) → bytea

Argument and return types are taken from the pg_proc catalog; internal type names are shown using their readable SQL spellings (for example int4 is shown as integer). (Derived from the catalog — see the linked reference for the canonical documentation.)

Classification

  • Category: Aggregate Functions
  • Kind: Aggregate function
  • Volatility: IMMUTABLE — Marked IMMUTABLE — it always returns the same result for the same arguments and can be used in indexes and other contexts that require immutability.
  • Returns: bytea, text

Example

Illustrative form (replace placeholder values with your own data):

SELECT string_agg(col) FROM your_table;

The example above is illustrative and is meant to show calling syntax only; consult the linked PostgreSQL documentation for exact semantics, edge cases and accepted argument combinations.

Version applicability

string_agg is present across the surveyed releases (PostgreSQL 15, 16). On older major versions, behaviour may differ in detail — always check the documentation for the version you run.

Related & references

Reference: PostgreSQL documentation — Aggregate Functions.