ESQL data types overview
A data type defines the characteristics of an item of data, and determines how that data is processed. ESQL supports six data types, listed later in this section. Data that is retrieved from databases, received in a self-defining message, or defined in a message model (using MRM data types), is mapped to one of these basic ESQL types when it is processed in ESQL expressions.
Within an integration node, the fields of a message contain data that has a definite data type. It is also possible to use intermediate variables to help process a message. You must declare all such variables with a data type before use. A variable's data type is fixed; If you try to assign values of a different type you get either an implicit cast or an exception. Message fields do not have a fixed data type, and you can assign values of a different type. The field adopts the new value and type.
It is not always possible to predict the data type that results from evaluating an expression. This is because expressions are compiled without reference to any kind of message schema, and so some type errors are not caught until run time.
ESQL defines the following categories of data. Each category contains one or more data types.