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Pull a random sample, and a stratified sample, for an ML training set in SQL.

Building a training set from a billion-row table means sampling, and the naive 'ORDER BY random() LIMIT n' sorts the whole table. Stratified sampling needs more care still. Here are both, done efficiently.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.

Building a training set from a billion-row table means sampling, and the naive 'ORDER BY random() LIMIT n' sorts the whole table. Stratified sampling needs more care still. Here are both, done efficiently.

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