select 1 as biaoshi from jdxtz where exists (
select * from gzpxx where gzpxx.bh=jdxtz.gzpbh and dqzt=‘借出‘
or exists( select * from xlgl where xlgl.bh=jdxtz.gsxlbh and dqzt=‘借出‘)
or exists( select * from gtxx where gtxx.bh=jdxtz.gsgtbh and dqzt=‘借出‘)
) and rownum<=1
or exists验证联合查询关联表是否存在存在则查询出信息
原文：https://www.cnblogs.com/java-llp/p/10858241.html