Queries

Queries are database operations that retrieve data from one or more tables or views. In Vertica, the top-level SELECT statement is the query, and a query nested within another SQL statement is called a subquery.

Vertica is designed to run the same SQL standard queries that run on other databases. However, there are some differences between Vertica queries and queries used in other relational database management systems.

The Vertica transaction model is different from the SQL standard in a way that has a profound effect on query performance. You can:

• Run a query on a static backup of the database from any specific date and time. Doing so avoids holding locks or blocking other database operations.
• Use a subset of the standard SQL isolation levels and access modes (read/write or read-only) for a user session.

In Vertica, the primary structure of a SQL query is its statement. Each statement ends with a semicolon, and you can write multiple queries separated by semicolons; for example:

=> CREATE TABLE t1( ..., date_col date NOT NULL, ...);
=> CREATE TABLE t2( ..., state VARCHAR NOT NULL, ...);