php - 如何选择在另一个表中具有最低值的 id？

Question

这就是我正在做的

SELECT * FROM pacient_export WHERE (idpacient_nit IN (SELECT idpacient FROM treatment WHERE date_treatment < CURDATE() - INTERVAL 180 DAY) OR idpacient_nit IN (SELECT idpacient FROM report7)) AND idpacient_nit IN (SELECT idpacient FROM report7 WHERE charge < 50)

SELECT * FROM pacient_export WHERE (idpacient_nit IN (SELECT idpacient FROM treatment WHERE date_treatment < CURDATE() - INTERVAL 180 DAY) OR idpacient_nit IN (SELECT idpacient FROM report7)) AND idpacient_nit IN (SELECT idpacient FROM report7 WHERE charge >= 50)

问题是在表report7中，一个pacient可以出现多次，它会多次选择同一个pacient...如何为每个pacient在表report7中选择最低收费值？

For example 
table: report7 
pacient | charge 
101 | 32 
101 | 92 

Results: 
pacient | charge 
101 | 32 

谢谢！！