SQL

In PostgreSQL, always use lowercase for object names (table names, column names) Reason In the database, uppercase and lowercase are distinguished when registering object names. In SQL, when enclosed in double quotes (" “), the exact string is used, but if not enclosed, the name is converted to lowercase (apparently). As a result, mismatches may occur. testdb=> \d iris Table "public.iris" Column | Type | Modifiers ---------------+-----------------------+----------- Id | integer | not null SepalLengthCm | numeric(15,2) | SepalWidthCm | numeric(15,2) | PetalLengthCm | numeric(15,2) | PetalWidthCm | numeric(15,2) | Species | character varying(20) | Indexes: "iris_pkey" PRIMARY KEY, btree ("Id") testdb=> select * from iris where SepalLengthCm > 5.0; --<--- NG ERROR: column "sepallengthcm" does not exist LINE 1: select * from iris where SepalLengthCm > 5.0; ^ HINT: Perhaps you meant to reference the column "iris.SepalLengthCm". testdb=> select * from iris where "iris.SepalLengthCm" > 5.0; --<--- NG ERROR: column "iris.SepalLengthCm" does not exist LINE 1: select * from iris where "iris.SepalLengthCm" > 5.0; ^ testdb=> select * from iris where "SepalLengthCm" > 5.0; --<--- OK testdb=> select * from iris where iris."SepalLengthCm" > 5.0; --<--- OK my previous blog post https://pumpkinpie-tea.blogspot.com/2016/06/postgresql.html ...