{"id":6095,"date":"2025-09-29T10:30:35","date_gmt":"2025-09-29T17:30:35","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/azure-sql\/?p=6095"},"modified":"2026-02-23T11:32:26","modified_gmt":"2026-02-23T19:32:26","slug":"data-api-builder-16-http-headers","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/azure-sql\/data-api-builder-16-http-headers\/","title":{"rendered":"Data API builder\u00a01.6: Advanced Behaviors with Special HTTP Headers"},"content":{"rendered":"

\n Data API builder (DAB) provides REST and GraphQL endpoints over SQL Server, Azure Cosmos DB, PostgreSQL, MySQL, and SQL Data Warehouse. REST endpoints support several HTTP headers that let you control how requests behave. These headers give you precision over updates, caching, and discovering new resources.\n<\/p>\n

\n If-Match\n<\/h2>\n

\n By default, DAB treats PUT<\/code> and PATCH<\/code> as upserts: update if the row exists, insert if not. Sometimes you need stricter semantics. If-Match<\/code> provides update-only behavior.\n<\/p>\n

\n If-Match<\/code> in DAB only supports *<\/code>. Any other value is rejected.\n<\/p>\n

\n
\n\n\n\n\n\n\n\n
\n Header value\n <\/th>\n\n Behavior\n <\/th>\n<\/tr>\n<\/thead>\n
\n If-Match: *<\/code>\n <\/td>\n\n Update only if the row exists; otherwise 404 Not Found<\/code>.\n <\/td>\n<\/tr>\n
\n Absent\n <\/td>\n\n Default upsert (insert if missing, update if found).\n <\/td>\n<\/tr>\n
\n Anything else\n <\/td>\n\n Rejected with 400 Bad Request<\/code>.\n <\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<\/div>\n

\n Example request that only updates if the row exists:\n<\/p>\n

\n
\n
\n
\n
PUT \/api\/Books\/id\/1\nIf-Match: *\nContent-Type: application\/json\n\n{\n  \"title\": \"The Return of the King\"\n}<\/code><\/pre>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/div>\n
\n  If the record exists, you get 200 OK<\/code>. If not, you get 404 Not Found<\/code>. This applies to both PUT<\/code> and PATCH<\/code>. DAB does not support ETag comparisons or concurrency tokens.\n<\/p>\n
\n  Read the documentation on If-Match<\/a>.\n<\/p>\n
\n  Cache-Control\n<\/h2>\n
\n  DAB can cache query results in memory or in a distributed cache. The Cache-Control<\/code> request header lets you override cache behavior. This applies only to DAB\u2019s cache, not browsers or CDNs.\n<\/p>\n
\n
\n\n\n\n\n\n\n\n\n
\n            Directive\n          <\/th>\n\n            Behavior\n          <\/th>\n<\/tr>\n<\/thead>\n
\n            no-cache<\/code>\n          <\/td>\n\n            Always query DB and refresh the cache.\n          <\/td>\n<\/tr>\n
\n            no-store<\/code>\n          <\/td>\n\n            Return cache if present; otherwise query DB but don\u2019t store.\n          <\/td>\n<\/tr>\n
\n            only-if-cached<\/code>\n          <\/td>\n\n            Return cached result only, else 504 Gateway Timeout<\/code>.\n          <\/td>\n<\/tr>\n
\n            Absent\n          <\/td>\n\n            Default: return cache if present, else query and cache.\n          <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
 Request example using <\/p>\n
    no-cache<\/code>. <\/p>\n
GET \/api\/Books\nCache-Control: no-cache\nAccept: application\/json<\/code><\/pre>\n<\/p><\/div>\n<\/div>\n
\n  Read the documentation on Cache headers<\/a>.\n<\/p>\n
\n  Location\n<\/h2>\n
\n  When you create a resource with POST<\/code>, DAB includes a Location<\/code> header showing the path of the new record. For PUT<\/code> or PATCH<\/code> that insert rows, it may be omitted.\n<\/p>\n