informatica lookup transformation

1. Lookup transformation finds matching values ​​from the database or flat file according to the input value; lookup transformation is divided into unconnected lookup and connected lookup.
1) Connected lookup: Multiple values ​​can be returned to other transformations through unconnected lookup. 2) Unconnected lookup can only return one value. Unconnected lookup uses: lkp.
  There is an R in lookup for return, which is for unconnected lookup of. You can check Output in the connected lookup.
Unconnected lookup: As a single transformation, it is not associated with other transformations through connections, and can only return a column, which is not connected with other expressions and called in expression.
unconnected lookup: not used in connection with other components, this can be understood as a function.
2 properties:
lookup cache persistent is generated on the server side. The cache is generated at the end of the first running session. The
lookup cache is divided into static and dynamic. As the name suggests, static is static, and dynamic is dynamic, which means that when the data source changes,
3.lookup will sort by default rules. If it is null and the value of lookup is also null, the match will be successful and no error will be reported.
If you don't want to use the ordering of the system default rules when you lookup, you should use "--" in sql override to shield the system defaults, and you can order them in the way you want. If you use your own sorting method without masking the default sorting method of the system, an error will be reported.
If you want to use lookup cache, you must check lookup caching enable
. If the lookup table name or the field contains keywords, it is recommended to use quotation marks.
The matching of lookup conditions:
  1) The ports on both sides of the condition must match
  2) Multiple conditions The relationship between and