COLUMN1;COLUMN2;COLUMN3;COLUMN4;COLUMN5;COLUMN6;COLUMN7
VALUE1;VALUE2;VALUE3;VALUE4;VALUE5;VALUE6;VALUE7;

Attachment csvFile = [SELECT Body FROM Attachment WHERE ParentId =: myFileId LIMIT 1];
String csvContent = csvFile.Body.toString();

Blob csvBlob = csvFile.Body;
String csvContent = EncodingUtil.base64Encode(csvBlob);