＃1054 - 在未知列'id.especialidades 'where子句'

Question

爲什麼查詢給我這個錯誤：＃1054 - 未知列 'id.especialidades' 在 'where子句'

SELECT * 

FROM medicos, especialidades 

WHERE id.especialidades = id_esp.medicos; 

Answer 1

You can refer to a column as col_name, tbl_name.col_name, or db_name.tbl_name.col_name. You need not specify a tbl_name or db_name.tbl_name prefix for a column reference unless the reference would be ambiguous. Refer to MySQL :: MySQL 5.0 Reference Manual :: 13.2.8 SELECT Syntax

表名應先列名。

SELECT * FROM medicos, especialidades 
WHERE especialidades.id = medicos.id_esp; 

Answer 2

你有條件寫下來。格式[table_name/alias].[attribute]

SELECT * 

FROM medicos, especialidades 

WHERE especialidades.id = medicos.id_esp;