如何正确使用UNIQUE索引? [英] how to use UNIQUE index correctly?

问题描述

我在DB上有4个字段，我将它们设置为不能重复的条目.它们是:

i have 4 fields at DB.i set them become cant duplicate entry.They are:

1. Model     Varchar(14)     Unique
2. Serial    varchar(8)      Unique
3. Lot       varchar(5)      Unique
4. Line      char(5)         Unique


                    Model         Serial             Lot             Line
First data        remocon         x0001              033a            fa 01

如果输入的数据相同，则无法记录.

and if i have inputed same data it can't recorded.

 remocon         x0001              033a            fa 01

但是如果我像这样输入，如何使该数据成功输入:

but how to make this data success to input if i type like:

remocon        x0002        033a            fa 01

我想要的结果是:

 Model         Serial             Lot             Line
remocon         x0001             033a            fa 01
remocon         x0002             033a            fa 01

推荐答案

您需要为所有字段(而不是每个字段)添加唯一约束，即

You need add unique constraint for all fields, not for each, i.e.

UNIQUE(型号，序列号，批次，行)

UNIQUE(Model, Serial, Lot, Line)

解决方案:

CREATE TABLE YourTable
(
 Model     Varchar(14)     NOT NULL,
 Serial    varchar(8)      NOT NULL,
 Lot       varchar(5)      NOT NULL,
 Line      char(5)         NOT NULL,
 unique    (model, serial, lot, line) 

)

对于现有表:

 alter table YourTableName drop index model;
 alter table YourTableName drop index serial;
 alter table YourTableName drop index lot;
 alter table YourTableName drop index line;
 alter table YourTableName add unique (model, serial, lot, line); 

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