JOIN

FS
select single BSTDK from VBKD where posnr = "000000" and vbeln = lips-VGBEL

Wrong:

SELECT SINGLE bstkd
      INTO m_output-bstkd
      FROM vbkd AS a INNER JOIN lips AS b ON a~vbeln = b~vgbel
      WHERE a~posnr EQ 000000.

Correct:

SELECT SINGLE bstkd
      INTO m_output-bstkd
      FROM vbkd AS a INNER JOIN lips AS b ON a~vbeln = b~vgbel
      WHERE a~posnr EQ 000000
      AND b~vbeln = m_output-vbeln_vl.

join只是把表连接在一起，数据筛选还是要放在Where之后