Database / Google Spanner Database Interview questions
What are the supported database dialects in Spanner?
Spanner databases are created with one of two dialects, chosen at creation time and fixed for the life of the database.
| GoogleSQL dialect | PostgreSQL dialect |
| Google's native SQL syntax, closest to standard SQL with Spanner-specific extensions. | PostgreSQL-compatible syntax and types, useful for teams migrating from Postgres. |
Data types like STRUCT and ARRAY are first-class. | Uses Postgres-style types such as bigint, numeric, and text. |
The choice affects DDL syntax, function names, and driver compatibility, so teams typically pick PostgreSQL dialect when porting an existing Postgres application and GoogleSQL when building new on Spanner or integrating with other Google Cloud tooling.
When is the database dialect chosen?
Which dialect is typically chosen when porting an existing Postgres app?
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