JOIN USING

USING Key Appears Once

The shared key appears once in the JOIN USING output.

highlighted = computed this step

USING key appears once

JOIN USING shows the shared key once in this teaching output layout.

shared key once\text{shared key once}

Read output shape

The JOIN USING output has 5 columns; the ON contrast has 6 columns because it keeps both key columns.

USING columns=5\text{USING columns}=5

JOIN USING examples are tiny finite-table transforms; SQL dialect completeness, type coercion, optimizer behavior, execution cost, indexing, output ordering guarantees, and database-product claims are out of scope.

USING key appears once: left tableorder_idcustomer_idnote110new220rush320gift4NULLdraft USING key appears once: right tablecustomer_idnamenote10Adavip20Benstandard20Bennyduplicate30CyprospectNULLUnknownmissing candidate key comparisonsleftSourcerightSourceleftKeyrightKeymatched001010yes011020no021020no031030no0410NULLno102010no112020yes122020yes132030no1420NULLno202010no212020yes222020yes232030no2420NULLno30NULL10no31NULL20no32NULL20no33NULL30no34NULLNULLno JOIN USING output rowscustomer_idleft.order_idleft.noteright.nameright.note101newAdavip202rushBenstandard202rushBennyduplicate203giftBenstandard203giftBennyduplicate ON join contrast rowsleft.order_idleft.customer_idleft.noteright.customer_idright.nameright.note110new10Adavip220rush20Benstandard220rush20Bennyduplicate320gift20Benstandard320gift20Bennyduplicate JOIN USING factsfactvalueleftRowCount4rightRowCount5candidatePairCount20matchingPairCount5matchedLeftRows3duplicateMatchRows2nullKeyCandidatePairs8usingKeyAppearsOnceyesduplicateNonKeyNames[note]outputColumnCount5onOutputColumnCount6rowOrderleft_source_then_right_source

One key column

The output header begins with customer id once, not left and right copies.

one shared key\text{one shared key}

Summary

The key output shape is the main JOIN USING difference shown here.

layout difference\text{layout difference}