1. v7.20 R0
Externals: Error handling
List und Label Multi-table

2. L&L: Debugging of externals
Problem
When an error occurs in an external of L&L, you don’t get any error when printing/previewing.
Only when opening the designer.
Example error
External$ ("$SQL select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref ='"+Job.customer.id+"'")
Correction
External$ ("$SQL select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref ='"+Job.customer.id+"' ) ")  

3. L&L: Good practice when creating externals
Use SQL to create and test query with example value: select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref = '100000')
Set the example value seperate select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref = ' ')
Change the example value with the FieldName select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref = ' + Job.customer.id + ')
Use double quotes for the sql text + this can be tested as a string in L&L.
"select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref = '" + Job.customer.id + "') "
Add function External$ ("$SQL select omschr__ from qalvl___ where qalvlref in (select qalvlref from klabas__ where kla__ref = '" + Job.customer.id+ "')")

4. L&L: Good practice when creating externals
New external to be created?
= Use an empty layout and copy afterwards
Quotes
Use of single quote (') is part of the sql statement to define values.
Use of double quote (") is to define the text parts of the SQL query.
Switch off Externals via ribbon?
= this is possible; but it is not stored and not indicated if switched on/off. DEMO