SQL: Intro
SQL (pronounced S-Q-L or SEQUEL) is a language designed to query relational databases- Used by most financial and commercial companies
- The result of an
SQL query is always a table
- It’s a nonprocedural language: define inputs and outputs; how the statement is executed is left to the optimizer
- How long SQL queries take depends on optimization that is opaque to user (which is great!)
SQL is a language that works with many (non-)commercial
products:
- Oracle Database, SQL Server (MS), MySQL, PostgreSQL, SQLite (all three open-source), Google BigQuery, Amazon Redshift…
- Performance will vary, but generally faster than standard data frame manipulation in R (and much more scalable)
dplyr is being slowly developed to work with databases