Structured Query Language , abbreviated as SQL ( (listen) S-Q-L ,
sometimes "sequel" for historical reasons), is a domain-specific language
used in programming and designed for managing data held in a relational
database management system (RDBMS), or for stream processing in a relational
data stream management system (RDSMS). It is particularly useful in handling
structured data, i.e. data incorporating relations among entities and
variables.
SQL offers two main advantages over older read–write APIs such as ISAM or
VSAM. Firstly, it introduced the concept of accessing many records with one
single command. Secondly, it eliminates the need to specify how to reach a
record, e.g. with or without an index.