medium10 pts · first answer countswindow-functionssql

Previous order from another customer

An analyst computes days since the previous order with LAG(order_date) OVER (ORDER BY customer_id, order_date). Some customers' first orders show a gap. Why?

A.LAG cannot handle date columns and returns the wrong typeB.ORDER BY with two columns is not allowed inside OVERC.LAG skips NULL dates and jumps further back in the tableD.With no PARTITION BY, LAG reads the previous customer's last order

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Previous order from another customer

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