字符集不匹配凝聚

Question

我有一個問題與此查詢，它告訴我的錯誤

ORA-00932: inconsistent datatypes: expected NCHAR got NUMBER 
00932.00000 - "inconsistent datatypes: expected% s got% s" 
* Cause: 
* Action: 
Error in line: 54, column: 43 

子查詢返回的字母「F」或在其中有更多學生的性別「M」這工作，但問題是我如何分配這封信給變量其中genero_a =

SELECT NOMBRE, COALESCE(DIRECCION,CORREO, 10) comm 
FROM ESTUDIANTE 
WHERE GENERO_A = 
    (SELECT GENERO_A 
    FROM ESTUDIANTE 
    GROUP BY GENERO_A 
    HAVING COUNT(GENERO_A) = 
     (SELECT MAX(COUNT(*)) as CONTAR 
     FROM ESTUDIANTE 
     GROUP BY GENERO_A)) 
ORDER BY NOMBRE; 

我不是SQL都精通，我感謝您的理解。

--TABLA ESTUDIANTE

CREATE TABLE ESTUDIANTE(
    ID_LECTOR VARCHAR2(50) NOT NULL, 
    NOMBRE VARCHAR2(50), 
    APELLIDO VARCHAR2(50), 
    GENERO_A CHAR(1) CONSTRAINT CH_GENERO_A CHECK(GENERO_A IN ('f', 'm')), 
    DIRECCION NVARCHAR2(100), 
    CORREO NVARCHAR2(50) 
); 
ALTER TABLE ESTUDIANTE ADD CONSTRAINT PK_ESTUDIANTE PRIMARY KEY(ID_LECTOR); 

Answer 1

錯誤是COALESCE(DIRECCION,CORREO, 10)，因爲所有的領域不具有相同的數據類型。

解決方案： 你要投NUMBER 10到類似的數據類型爲導向，以郵報的。 只需將上面的代碼更改爲COALESCE(DIRECCION,CORREO, CAST(10 as NVARCHAR2(2)))即可。

CAST函數將一個數據類型的值轉換爲另一個數據類型。

更新查詢：

SELECT NOMBRE, COALESCE(DIRECCION,CORREO, CAST(10 as NVARCHAR2(2))) comm 
FROM ESTUDIANTE 
WHERE GENERO_A = 
    (SELECT GENERO_A 
    FROM ESTUDIANTE 
    GROUP BY GENERO_A 
    HAVING COUNT(GENERO_A) = 
     (SELECT MAX(COUNT(*)) as CONTAR 
     FROM ESTUDIANTE 
     GROUP BY GENERO_A)) 
ORDER BY NOMBRE; 

或者，從您提供的link，

SELECT NOMBRE, COALESCE(DIRECCION,CORREO, N'10') comm 
FROM ESTUDIANTE 
WHERE GENERO_A = 
    (SELECT GENERO_A 
    FROM ESTUDIANTE 
    GROUP BY GENERO_A 
    HAVING COUNT(GENERO_A) = 
     (SELECT MAX(COUNT(*)) as CONTAR 
     FROM ESTUDIANTE 
     GROUP BY GENERO_A)) 
ORDER BY NOMBRE; 

或者，

SELECT NOMBRE, COALESCE(DIRECCION,CORREO, N''||10) comm 
FROM ESTUDIANTE 
WHERE GENERO_A = 
    (SELECT GENERO_A 
    FROM ESTUDIANTE 
    GROUP BY GENERO_A 
    HAVING COUNT(GENERO_A) = 
     (SELECT MAX(COUNT(*)) as CONTAR 
     FROM ESTUDIANTE 
     GROUP BY GENERO_A)) 
ORDER BY NOMBRE;