data // SQLPRODUCTION

UNION ALL for Multi-Source Staging

Normalize multiple source populations into one staging shape without deduplicating too early.

sqlunion allmultibrandstaging

Trust & provenancePRODUCTION

Evidence tierPRODUCTIONOfficial sources0Other sources0Last verified2026-10-05

Evidence tier describes my hands-on relationship with the content. Official sources describe platform contracts/documentation. Production observations should not automatically be treated as official limits.

EvidencePRODUCTION

Difficultyintermediate

Verified2026-10-05

Use when

Combining brands or legacy source tables before identity resolution.

SELECT
    SubscriberKey,
    EmailAddress,
    'BRAND_A' AS SourceBrand
FROM [BrandA_Customers]

UNION ALL

SELECT
    SubscriberKey,
    EmailAddress,
    'BRAND_B' AS SourceBrand
FROM [BrandB_Customers]

Why it works

UNION ALL preserves every row and avoids the implicit deduplication cost/behavior of UNION.

Operational notes

Normalize compatible data types and field lengths across every SELECT branch.

Deduplicate after source lineage has been preserved.

ROW_NUMBER() with Business Priority

Choose a surviving customer row by source trust first, recency second.

→

UNION ALL for Multi-Source Staging

Keep following the context.