Structured query language
One language that you use to access the data in IMS™ is SQL. SQL is a standardized language for defining and manipulating data in a relational database.
The language consists of SQL statements. SQL statements let you retrieve, insert, update, or delete data in IMS databases.
When you write an SQL statement, you specify what you want done, not how to do it. To access data, for example, you need only to name the segment and fields that contain the data. You do not need to describe how to get to the data.
In accordance with the relational model of data:
- The database is perceived as a set of tables.
- Relationships are represented by values in tables.
- Data is retrieved by using SQL to specify a result table that can be derived from one or more tables.
IMS transforms each SQL statement, that is, the specification of a result table, into a sequence of operations for data retrieval or modifications.
All executable SQL statements must be prepared before they can run.
- Static SQL
The source form of a static SQL statement is embedded within an application program that is written in a host language such as COBOL. The statement is prepared before the program is executed and the operational form of the statement persists beyond the execution of the program. - Dynamic SQL
Programs that contain embedded dynamic SQL statements must be precompiled like those that contain static SQL, but unlike static SQL, the dynamic statements are constructed and prepared at run time. - Interactive SQL
Interactive SQL refers to SQL statements submitted using IMS Enterprise Suite Explorer for Development.