需求：原本是定义5个字段存储的类型全部都是 数字类型，后来需求变了，每个字段可能存储粘接类型 如：135/200这种格式

原本的数据表结构：

CREATE TABLE MTG_SOC_MEASURE(

    PKEY NUMBER(10,0),

    MTG_EQUIP_INFO_PTR NUMBER(10,0),  --机器信息，指向MTG_EQUIP_INFO 

    CUSTOMER_PART_NUMBER VARCHAR2(35), --生产型号，指向DATA0050

    WORK_ORDER_NUMBER    VARCHAR2(50),--工单号

    FACE_TIME  VARCHAR(10),  --面次  TOP  BOT

    TTYPE  VARCHAR2(30),     --类别:1代表“首板”,2代表“过程监控”

    SIZE_REQUIREMENTS VARCHAR(10),--尺寸要求

    MEASURE_1  NUMBER(10,3),

    MEASURE_2  NUMBER(10,3),

    MEASURE_3  NUMBER(10,3),

    MEASURE_4  NUMBER(10,3),

    MEASURE_5  NUMBER(10,3),

}

现在需要把 MEASURE_1、 MEASURE_2、 MEASURE_3、 MEASURE_4、 MEASURE_5数据类型改为VARCHAR2(50),但是表已经存在记录，因此需要中间字段进行操作，才能实现，分为以下5个步骤，如下：

--第一步，在表中加一个临时字段

alter table MTG_SOC_MEASURE add MEASURE_1_T   NUMBER(10,3);

alter table MTG_SOC_MEASURE add MEASURE_2_T   NUMBER(10,3);

alter table MTG_SOC_MEASURE add MEASURE_3_T   NUMBER(10,3);

alter table MTG_SOC_MEASURE add MEASURE_4_T   NUMBER(10,3);

alter table MTG_SOC_MEASURE add MEASURE_5_T   NUMBER(10,3);

--第二步，将目标字段的值付给临时字段，并将目标字段置空

update MTG_SOC_MEASURE set MEASURE_1_T=MEASURE_1,MEASURE_1=null;

update MTG_SOC_MEASURE set MEASURE_2_T=MEASURE_2,MEASURE_2=null;

update MTG_SOC_MEASURE set MEASURE_3_T=MEASURE_3,MEASURE_3=null;

update MTG_SOC_MEASURE set MEASURE_4_T=MEASURE_4,MEASURE_4=null;

update MTG_SOC_MEASURE set MEASURE_5_T=MEASURE_5,MEASURE_5=null;

--第三步，修改目标类型

alter table MTG_SOC_MEASURE  modify MEASURE_1 varchar2(50);

alter table MTG_SOC_MEASURE  modify MEASURE_2 varchar2(50);

alter table MTG_SOC_MEASURE  modify MEASURE_3 varchar2(50);

alter table MTG_SOC_MEASURE  modify MEASURE_4 varchar2(50);

alter table MTG_SOC_MEASURE  modify MEASURE_5 varchar2(50);

--第四步，将临时字段的值付给目标字段，并将临时字段置空

update MTG_SOC_MEASURE set MEASURE_1=MEASURE_1_T,MEASURE_1_T=null;

update MTG_SOC_MEASURE set MEASURE_2=MEASURE_2_T,MEASURE_2_T=null;

update MTG_SOC_MEASURE set MEASURE_3=MEASURE_3_T,MEASURE_3_T=null;

update MTG_SOC_MEASURE set MEASURE_4=MEASURE_4_T,MEASURE_4_T=null;

update MTG_SOC_MEASURE set MEASURE_5=MEASURE_5_T,MEASURE_5_T=null;

--第五步，最后一步，删除临时字段

alter table MTG_SOC_MEASURE drop column MEASURE_1_T;

alter table MTG_SOC_MEASURE drop column MEASURE_2_T;

alter table MTG_SOC_MEASURE drop column MEASURE_3_T;

alter table MTG_SOC_MEASURE drop column MEASURE_4_T;

alter table MTG_SOC_MEASURE drop column MEASURE_5_T;

 

修改后的表结构如下;

PKEY                 NOT NULL NUMBER(10)   

MTG_EQUIP_INFO_PTR            NUMBER(10)   

CUSTOMER_PART_NUMBER          VARCHAR2(35) 

WORK_ORDER_NUMBER             VARCHAR2(50) 

FACE_TIME                     VARCHAR2(10) 

TTYPE                         VARCHAR2(30) 

SIZE_REQUIREMENTS             VARCHAR2(50) 

MEASURE_1                     VARCHAR2(50) 

MEASURE_2                     VARCHAR2(50) 

MEASURE_3                     VARCHAR2(50) 

MEASURE_4                     VARCHAR2(50) 

MEASURE_5                     VARCHAR2(50)