If you're concerned about the data select efficiency, have an index on LFART, and replace the exists with a hardcoded IN. That won't work, of course, if your desired values of LFART are being loaded earlier in the script, but if it's just a few values, it should work fine:
[LIKP]: Load MANDT, VBELN, VKORG, WADAT, LFART, KUNNR; SQL SELECT MANDT VBELN VKORG WADAT LFART KUNNR from LIKP WHERE LFART IN ('ZLI','ZLD');