A Microsoft extension to the ANSI SQL language that includes procedural programming, local variables, and various support functions.
Try this:
DECLARE @Bluemchen TABLE (Loc VARCHAR(100),PO VARCHAR(100),Item VARCHAR(100),wt VARCHAR(100),Stat INT, qty VARCHAR(100));
INSERT INTO @tbl VALUES
('CL','000587408','790121','0','10','450'),
('CL','000587409','790121','0','10','120'),
('CL','000587410','790121','0','10','450'),
('CL','000587411','790121','0','10','450'),
('PCS','000590064','790121','4200','90','70'),
('CL','000590064','790121','0','10','450'),
('PCS','000590064','790121','6300','90','105'),
('PCS','000590065','790121','6300','90','0'),
('PCS','000590065','790121','0','10','1'),
('PCS','000590065','790121','4200','90','70'),
('PCS','000590065','790121','4140','90','0'),
('PCS','000590065','790121','6300','90','105'),
('PCS','000590065','790121','60','40','0'),
('CL','000590065','790121','0','10','450'),
('PCS','000590065','790121','4140','90','70'),
('PCS','000590066','790121','12600','90','210'),
('PCS','000590066','790121','4200','90','70'),
('CL','000590066','790121','28560','90','476'),
('FP','000590066','790121','18900','90','315'),
('CL','000590067','790121','28620','90','477'),
('CL','000591787','790121','0','10','500'),
('CL','000591788','790121','0','10','500'),
('CL','000591789','790121','0','10','500'),
('CL','000591790','790121','28320','90','472');
SELECT *
FROM @tbl
WHERE PO IN (
SELECT PO
FROM @tbl
GROUP BY PO
HAVING MAX(Stat) < 40
)