利用JSON_ARRAYAGG解决问题 -＞ ORA-01489: result of string concatenation is too long

不念不忘少年蓝@ 2024-03-27 15:32 6阅读 0赞

**问题： ORA-01489: result of string concatenation is too long**

#### 1. 查看Oracle数据库版本 ####

如果数据库版本为18c或更高版本，则可以使用json\_arrayagg替代xmlagg

SELECT * FROM V$VERSION;

#### 2. 由于Oracle数据库版本是19c，所以使用JSON\_ARRAYAGG ####

##### 2.1 数据准备 #####

创建students表，为后续演示JSON\_ARRAYAGG功能做准备

DROP TABLE students;
    COMMIT;
    
    CREATE TABLE students
        ( student_id     NUMBER(6)
        , first_name     VARCHAR2(20)
        , last_name      VARCHAR2(25) 
        , email          VARCHAR2(40) 
        , phone_number   VARCHAR2(20)
        , join_date      DATE 
        , class_id       VARCHAR2(20)  
        , fees           NUMBER(8,2)
        , professor_id   NUMBER(6)
        , department_id  NUMBER(4) 
        ) ;
        
    CREATE UNIQUE INDEX stu_id_pk ON students (student_id) ;
    INSERT INTO students VALUES (100,'SMITH','JAMES','SMITH.JAMES@notreal.com','111.111.1245',TO_DATE('17-06-2003','DD-MM-YYYY'),'INS_CHAIRMAN',24000,NULL,NULL);
    INSERT INTO students VALUES (101,'JOHNSON','JOHN','JOHNSON.JOHN@notreal.com','111.111.1246',TO_DATE('21-09-2005','DD-MM-YYYY'),'INS_VP',17000,100,90);
    INSERT INTO students VALUES (102,'WILLIAMS','ROBERT','WILLIAMS.ROBERT@notreal.com','111.111.1247',TO_DATE('13-01-2001','DD-MM-YYYY'),'INS_VP',17000,100,90);
    INSERT INTO students VALUES (103,'BROWN','MICHAEL','BROWN.MICHAEL@notreal.com','111.111.1248',TO_DATE('03-01-2006','DD-MM-YYYY'),'INS_STAFF',9000,102,60);
    INSERT INTO students VALUES (104,'JONES','WILLIAM','JONES.WILLIAM@notreal.com','111.111.1249',TO_DATE('21-05-2007','DD-MM-YYYY'),'INS_STAFF',6000,103,60);
    INSERT INTO students VALUES (105,'MILLER','DAVID','MILLER.DAVID@notreal.com','111.111.1250',TO_DATE('25-06-2005','DD-MM-YYYY'),'INS_STAFF',4800,103,60);
    INSERT INTO students VALUES (106,'DAVIS','RICHARD','DAVIS.RICHARD@notreal.com','111.111.1251',TO_DATE('05-02-2006','DD-MM-YYYY'),'INS_STAFF',4800,103,60);
    INSERT INTO students VALUES (107,'GARCIA','CHARLES','GARCIA.CHARLES@notreal.com','111.111.1252',TO_DATE('07-02-2007','DD-MM-YYYY'),'INS_STAFF',4200,103,60);
    INSERT INTO students VALUES (108,'RODRIGUEZ','JOSEPH','RODRIGUEZ.JOSEPH@notreal.com','111.111.1253',TO_DATE('17-08-2002','DD-MM-YYYY'),'CL_PHY',12008,101,100);
    INSERT INTO students VALUES (109,'WILSON','THOMAS','WILSON.THOMAS@notreal.com','111.111.1254',TO_DATE('16-08-2002','DD-MM-YYYY'),'CL_MATH',9000,108,100);
    INSERT INTO students VALUES (110,'MARTINEZ','CHRISTOPHER','MARTINEZ.CHRISTOPHER@notreal.com','111.111.1255',TO_DATE('28-09-2005','DD-MM-YYYY'),'CL_MATH',8200,108,100);
    INSERT INTO students VALUES (111,'ANDERSON','DANIEL','ANDERSON.DANIEL@notreal.com','111.111.1256',TO_DATE('30-09-2005','DD-MM-YYYY'),'CL_MATH',7700,108,100);
    INSERT INTO students VALUES (112,'TAYLOR','PAUL','TAYLOR.PAUL@notreal.com','111.111.1257',TO_DATE('07-03-2006','DD-MM-YYYY'),'CL_MATH',7800,108,100);
    INSERT INTO students VALUES (113,'THOMAS','MARK','THOMAS.MARK@notreal.com','111.111.1258',TO_DATE('07-12-2007','DD-MM-YYYY'),'CL_MATH',6900,108,100);
    
    COMMIT;

##### 2.2 利用JSON\_ARRAYAGG进行拼接字符串 #####

SELECT class_id,
          replace(JSON_ARRAYAGG(first_name || ' ' || last_name ORDER BY class_id RETURNING CLOB),'"','') AS retunring_val
    FROM students
    GROUP BY class_id;
    -------------------------------------------------
    输出结果：
    CL_MATH         [WILSON THOMAS,THOMAS MARK,TAYLOR PAUL,ANDERSON DANIEL,MARTINEZ CHRISTOPHER]
    CL_PHY          [RODRIGUEZ JOSEPH]
    INS_CHAIRMAN    [SMITH JAMES]
    INS_STAFF       [BROWN MICHAEL,GARCIA CHARLES,DAVIS RICHARD,MILLER DAVID,JONES WILLIAM]
    INS_VP          [JOHNSON JOHN,WILLIAMS ROBERT]

这里SQL展示了JSON\_ARRAYAGG的基本用法，即将first\_name与last\_name进行拼接，其他详细配置请参考[SQL聚合函数 JSON\_ARRAYAGG][SQL_ JSON_ARRAYAGG]

注：**CLOB** 是内置类型，它将字符大对象 (Character Large Object) 存储为数据库表某一行中的一个列值.

#### 3. 对JSON\_ARRAYAGG查询结果进行处理 ####

##### 3.1 利用TRIM()去除首尾部的\[\]并替换’,‘为’;’ #####

WITH TEMP AS (SELECT CLASS_ID,
                         TRIM(REPLACE(JSON_ARRAYAGG(FIRST_NAME || ' ' || LAST_NAME ORDER BY CLASS_ID RETURNING CLOB), '"',
                                      '')) AS RETUNRING_VAL
                  FROM STUDENTS
                  GROUP BY CLASS_ID)
    SELECT REPLACE(TRIM(TRAILING ']' FROM
                        TRIM(LEADING '[' FROM RETUNRING_VAL)), ',', ';') AS RETUNRING_VAL
    FROM TEMP;

#### 4.解决问题时遇到的小知识点 ####

##### 4.1 listagg()列转行函数如果长度超过4000，会报Error，解决方法是LISTAGG(CAST(NAME AS VARCHAR(10000)), ‘,’) #####

##### 4.2 Trim()参数 #####

*  LEADING 开头字符
 *  TRAILING 结尾字符
 *  BOTH 开头和结尾字符

##### 4.3 CAST可以将一种类型转换为另外一种类型 #####

SELECT CAST('123.4567' AS NUMBER(10,2))  AS NUM FROM DUAL;

[SQL_ JSON_ARRAYAGG]: https://blog.csdn.net/yaoxin521123/article/details/122164799