Friday, 10 January 2014

ESQL statements and what they do

ESQL statements

You can use ESQL statements to manipulate message trees, update databases, or interact with nodes.
The following table summarizes the ESQL statements and what they do.
Statement type
Description
Basic statements:
Gives the statements defined within the BEGIN and END keywords the status of a single statement.
Invokes a user-written routine that has been defined using a CREATE FUNCTION or CREATE PROCEDURE statement.
Uses rules defined in WHEN clauses to select a block of statements to execute.
Like CREATE PROCEDURE, CREATE FUNCTION defines a user-written routine. (The few differences between CREATE FUNCTION and CREATE ROUTINE are described in the reference material.)
Creates a module (a named container associated with a node).
Like CREATE FUNCTION, CREATE PROCEDURE defines a user-written routine. (The few differences between CREATE FUNCTION and CREATE ROUTINE are described in the reference material.)
Declares one or more variables that can be used to store temporary values.
Processes a set of statements based on the result of evaluating condition expressions.
Abandons processing the current iteration of the containing WHILE, REPEAT, LOOP, or BEGIN statement, and might start the next iteration.
Abandons processing the current iteration of the containing WHILE, REPEAT, LOOP or BEGIN statement, and stops looping.
Processes a sequence of statements repeatedly and unconditionally.
Processes a sequence of statements, then evaluates a condition expression. If the expression evaluates to TRUE, executes the statements again.
Stops processing the current function or procedure and passes control back to the caller.
Evaluates a source expression, and assigns the result to the target entity.
Generates a user exception.
Evaluates a condition expression, and if it is TRUE executes a sequence of statements.
Message tree manipulation statements:
Attaches a portion of a message tree into a new position in the message hierarchy.
Creates a new message field.
Detaches and destroys a portion of a message tree, allowing its memory to be reused.
Detaches a portion of a message tree without deleting it.
Iterates through a list (for example, a message array).
Changes the field pointed to by a target reference variable.
Database update statements:
Deletes rows from a table in an external database based on a search condition.
Adds a new row to an external database.
Takes a character value and passes it as an SQL statement to an external database.
Updates the values of specified rows and columns in a table in an external database.
Node interaction statements:
Propagates a message to the downstream nodes within the message flow.
Other statements:
This statement is optional and is used in an ESQL file to explicitly identify the schema that contains the file.
Declares an error handler.
Takes a character value, interprets it as an SQL statement, and executes it.
Writes a record to the event or user trace log.
Re-throws the current exception (if any). This is used by an error handler, when it cannot handle an exception, to give an error handler in higher scope the opportunity of handling the exception.

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