SQL query structure

SQL includes Data Definition Language (DDL) statements and Data Manipulation Language (DML) statements.

DDL statements, such as CREATE, ALTER, and DROP, modify the schema of a database. DML statements, such as SELECT, INSERT, UPDATE, and DELETE, manipulate data in tables.

SELECT something FROM some table
   WHERE some conditions are satisfied

UPDATE some table SET something
   WHERE some conditions are satisfied

The italicized components serve different purposes in the DML query. The some table part is called “the from list” and is not important to consider when you design a DataBlade module. The something part is called “the target list” and identifies the columns for retrieval or update. The target list is the target on which the query is operating. The some conditions are satisfied part of the query is called “a qualification” because it identifies the rows that qualify to participate in the operation.

When you develop a DataBlade module, consider where you expect a particular routine to be used. In the following two sections, the DataBlade module routines that typically appear in the target list and qualification are addressed.