sql=''' select * from st where loc = 'nchar0' limit 1 union all select * from st where loc = 'nchar1' limit 1 union all select * from st where loc = 'nchar2' limit 1
sql=''' select * from st where loc = 'nchar0' limit 1 union all select * from st where loc = 'nchar1' limit 1 union all select * from st where loc = 'nchar2' limit 1
union all select * from st where loc = 'nchar3' limit 1 union all select * from st where loc = 'nchar4' limit 1 union all select * from st where loc = 'nchar5''''
union all select * from st where loc = 'nchar3' limit 1 union all select * from st where loc = 'nchar4' limit 1 union all select * from st where loc = 'nchar5' limit 1'''