您可能会有处理包含分隔子字段的消息的消息流。如果您知道子字段的定界符,可以编码 ESQL 从周围的上下文抽取该子字段。
如果您创建执行此任务的函数,或者类似的函数,则可以从 ESQL 模块(Compute、Database 和 Filter 节点中的)和映射文件(DataDelete、DataInsert、DataUpdate、Extract、Mapping 和 Warehouse 节点所使用的)调用它。
以下函数示例抽取了由特定字符分隔的特定消息子字段。
CREATE FUNCTION SelectSubField (SourceString CHAR, Delimiter CHAR, TargetStringPosition INT) RETURNS CHAR -- This function returns a substring at parameter position TargetStringPosition within the -- passed parameter SourceString. An example of use might be: -- SelectSubField(MySourceField,' ',2) which will select the second subfield from the -- field MySourceField delimited by a blank. If MySourceField has the value -- "First Second Third" the function will return the value "Second" BEGIN DECLARE DelimiterPosition INT; DECLARE CurrentFieldPosition INT 1; DECLARE StartNewString INT 1; DECLARE WorkingSource CHAR SourceString; SET DelimiterPosition = POSITION(Delimiter IN SourceString); WHILE CurrentFieldPosition < TargetStringPosition DO IF DelimiterPosition = 0 THEN -- DelimiterPosition will be 0 if the delimiter is not found -- exit the loop SET CurrentFieldPosition = TargetStringPosition; ELSE SET StartNewString = DelimiterPosition + 1; SET WorkingSource = SUBSTRING(WorkingSource FROM StartNewString); SET DelimiterPosition = POSITION(Delimiter IN WorkingSource); SET CurrentFieldPosition = CurrentFieldPosition + 1; END IF; END WHILE; IF DelimiterPosition > 0 THEN -- Remove anything following the delimiter from the string SET WorkingSource = SUBSTRING(WorkingSource FROM 1 FOR DelimiterPosition); SET WorkingSource = TRIM(TRAILING Delimiter FROM WorkingSource); END IF; RETURN WorkingSource; END;