sql数据从何处获取的

问题遇到的现象和发生背景

最近公司项目重构，研究老代码，分析sql时遇到一个问题，不太理解，请教一下各位

UPDATE
    ZCZJJS ZCZJ
SET
    (F_FSJFYZ,
    F_FSDFYZ,
    F_FSJFZJ,
    F_FSDFZJ,
    F_FSJFJZ,
    F_FSDFJZ) = (
    SELECT
        F_FSJFYZ,
        F_FSDFYZ,
        F_FSJFZJ,
        F_FSDFZJ,
        F_FSJFJZ,
        F_FSDFJZ
    FROM
        sinojzbm.ZCFSSJ
    WHERE
        F_KJQJ = ZCZJ.F_KJQJ
        AND F_GUID = ZCZJ.F_GUID
        AND F_ZJZCBH = ZCZJ.F_ZJZCBH)
WHERE
     F_CODE = '1000100110011001'
    AND F_KJQJ = '202201'
    AND F_ZJZCBH IN ('01');

是看的sinojzbm库里的ZCFSSJ表吗？把边select语句单独执行下