ABAP+在select的时候，可以A=B A=C B=C这样子JOIN吗？

可以，代码如下：

INNER JOIN T030 ON T030~BKLAS = MBEW~BKLAS AND T030~BWMOD = T001K~BWMOD

完整代码示例：

 SELECT
      T030~KONTS,
      SKAT~TXT20,
      MBEW~MATNR,
      MBEW~BWKEY
      FROM MBEW
      INNER JOIN T001K ON  T001K~BWKEY = MBEW~BWKEY  "评估分组代码
      INNER JOIN T030 ON  T030~BKLAS = MBEW~BKLAS   AND T030~BWMOD = T001K~BWMOD
      LEFT JOIN SKAT ON skat~SAKNR = T030~KONTS AND skat~KTOPL = T030~KTOPL
      FOR ALL ENTRIES IN @GT_TAB
      WHERE T030~KTOSL = 'BSX'
      AND T030~KTOPL = '1000'
      AND MBEW~MATNR = @GT_TAB-MATNR
      AND MBEW~BWKEY = @GT_TAB-WERKS
    INTO TABLE @DATA(LT_T030).

另外，写了一篇比较全面的SAP select查询的笔记，可移步查看：

【案例总结】简直绝了------非常全面的SELECT总结_select comp.code as bukrs, plat.code as werks, a.o-CSDN博客