Beginning Database with Postgresql reading notebook 1 flat files : repeating groups spreadsheets : can not support multiuser access ; strict two deminsions basic rules for designing tables : 1. break down the data into columns 2. have a unique way of identify each row 3. remove repeating information 4. get the naming right with n2n relationship create a third table bettwen the two tables Date Types : serial,char,varchar,date,numeric specially notice the NULLs 原文链接：https://www.f2er.com/postgresql/197330.html