SnowPro COF-C02 SQL and Semi-Structured Data Guide
April 14, 2026
Study SnowPro COF-C02 SQL and Semi-Structured Data: key concepts, common traps, and exam decision cues.
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This lesson matters because COF-C02 still expects comfort with ordinary SQL tables and DML, but it also expects you to know when a nested payload belongs in VARIANT and when FLATTEN is the signal that array-like content must expand.
Data-shape chooser
If the question is mostly about…
Strongest first fit
rows, columns, joins, and merges
structured SQL
nested JSON-like payloads
semi-structured logic
expanding arrays or nested elements
FLATTEN awareness
Start with the shape of the data
Data shape
Stronger first instinct
relational rows and columns
structured SQL lane
nested payload kept as one semi-structured value
VARIANT
nested array elements need row expansion
FLATTEN
The shape tells you the answer family before you think about function names.
Decision order that usually wins
Identify whether the payload is structured or semi-structured.
If it is nested JSON-like content, think VARIANT.
If nested array elements must become rows, think FLATTEN.
If the task is ordinary joins or merges, stay in structured SQL.