Control Flow

GSQL provides standard control flow statements that can be used at the Query Body level (top-level logic) or the DML-Sub level (inside clauses like ACCUM).

1. Conditional Logic

IF...ELSE

Standard branching logic. Use THEN and END to wrap blocks.

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IF @@num_friends > 10 THEN
  PRINT "Popular User";
ELSE IF @@num_friends > 0 THEN
  PRINT "Active User";
ELSE
  PRINT "Quiet User";
END;

CASE Statement

Supports both "Switch-style" and "Conditional-style" logic.

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# Switch-style
CASE v.gender
  WHEN "Male" THEN @@males += 1
  WHEN "Female" THEN @@females += 1
  ELSE @@unknown += 1
END;

# Conditional-style
CASE
  WHEN v.age < 18 THEN @@minors += 1
  WHEN v.age >= 18 THEN @@adults += 1
END;

2. Iterative Logic

WHILE Loop

Iterates until a condition is false. Use an optional LIMIT to prevent infinite loops.

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WHILE visited_vertices.size() > 0 LIMIT 10 DO
  visited_vertices = SELECT t
                     FROM visited_vertices:s -(:e)-> :t
                     WHERE t.@visited == false
                     POST-ACCUM t.@visited = true;
END;

FOREACH Loop

Iterates over a range or a collection (List, Set, Bag).

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# Range-based
FOREACH i IN RANGE[0, 5] DO
  @@sum += i;
END;

# Collection-based
FOREACH item IN @@my_list DO
  PRINT item;
END;

3. Loop Control

• BREAK: Exits the current loop immediately.
• CONTINUE: Skips the rest of the current iteration and starts the next one.

[!IMPORTANT] Query-Body vs. DML-Sub: Statements at the query-body level end with a semicolon (;). Statements inside a DML clause (like ACCUM) are comma-separated.