字符集不匹配合并

Question

这个查询有问题，它告诉我错误

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

子查询 returns 学生性别的字母 "f" 或 "m" 其中有更多，这可行，但问题是我如何将该字母分配给变量 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;

我一点都不精通sql，感谢您的理解。

--学生桌

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

错误出现在 COALESCE(DIRECCION,CORREO, 10)，因为所有字段的数据类型不同。

解法： 您必须将 NUMBER 10 转换为与 DIRECTION 和 CORREO 类似的数据类型。只需将上面的代码更改为 COALESCE(DIRECCION,CORREO, CAST(10 as NVARCHAR2(2))).

The CAST function converts a value from one data type to another.

更新查询：

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，根据您提供的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;

字符集不匹配合并

character set mismatch coalesce

sql

oracle

oracle-sqldeveloper