Usage of Dual table

If the select query involves fetching data from multiple tables then we use dual table.

AND 0=(SELECT COUNT(*) FROM DUAL WHERE TBUONE.TBUNAME = 'TOC-NY' AND RTT.CODE = 'LACP-OAP' AND CD1.COUNTRYCODE = 'KR' AND RD.AUTOAPPROVEDFLAG = 'N' AND RD.AMOUNT < 500000)