今天遇到一個問題,Postgre的一個查詢功能突然報錯“ERROR: UNION types numeric and character varying cannot be matched,LINE 6: ...ipematerial,b.geom,b.pressurerating,b.pipelength, pipediam,b...”,在對兩個結果集進行合並查詢時報錯,數字和字符串的類型不能合並,SQL如下:
SELECT a.gid AS gid, a. NAME AS NAME, a.pipematerial, a.geom, a.pressurerating, a.pipelength, a.pipediam, a.wallthickness, a.source, a.target FROM zy a WHERE a.projectId = '2c91808f7cc0e652017ccfc7f7ea016f' UNION ALL SELECT b.id AS gid, b. NAME AS NAME, b.pipematerial, b.geom, b.pressurerating, b.pipelength, b.pipediam, b.wallthickness, b.source, b.target FROM digital_edit_pipeline b WHERE b.condition_id = '2c9180887d45f311017d55857e9b02ac' AND b. ENABLE = 1
查了一下,是digital_edit_pipeline 表的pipediam字段被改成了字符串類型,這是另外一個同事出於某種原因進行了修改,導致這個地方報錯了,解決也很簡單,把兩個表的這個字段轉換成相同的數據類型就可以了,用to_number (obj, '99999.999')就可以把字符串轉數字,修改后的SQL如下:
SELECT a.gid AS gid, a. NAME AS NAME, a.pipematerial, a.geom, a.pressurerating, a.pipelength, a.pipediam, a.wallthickness, a.source, a.target FROM zy a WHERE a.projectId = '2c91808f7cc0e652017ccfc7f7ea016f' UNION ALL SELECT b.id AS gid, b. NAME AS NAME, b.pipematerial, b.geom, b.pressurerating, b.pipelength, to_number (b.pipediam, '99999.999') AS pipediam, b.wallthickness, b.source, b.target FROM digital_edit_pipeline b WHERE b.condition_id = '2c9180887d45f311017d55857e9b02ac' AND b. ENABLE = 1
如上,就可以解決之前的報錯了。如果需要截取字符串后再轉數字,可以用trim()函數,如trim(both 'abc' from pipediam),可以去除pipediam字段中包含abc的字符串,完整的書寫就是to_number(trim(both 'abc' from pipediam), '9999.999') AS pipediam。
其實不管是Postgre還是MySQL、Oracle等其他數據,這個解決思路都是一樣,差別可能就是每個數據庫的函數不太一樣。