Обсуждение: Left join

Hi, all,

I tried to use "left join" to select data from my
database. Result is come out, but I didn't see the
value of "displayString". I added "left outer join",
same result.

SELECT   devices.ProductType,  devices.deviceKey,
devices.fullDNSName, deviceTypesEnum.displayString,
deviceTypesEnum.enumId FROM devices
 LEFT JOIN deviceTypesEnum ON  deviceTypesEnum.enumId
= devices.productType;


Can anyone tell me how to modify this query?

Thanks a lot!

Zengfa

[root@scmlin46 data]# psql -Umxadmin mydb_v1_0;
Welcome to psql 7.3.2, the PostgreSQL interactive
terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit

mydb=# SELECT   devices.ProductType,
devices.deviceKey, devices.fullDNSName,
deviceTypesEnum.displayString, deviceTypesEnum.enumId
FROM devices
mysql=#  LEFT JOIN deviceTypesEnum ON
deviceTypesEnum.enumId = devices.productType;
 producttype | devicekey |    fulldnsname     |
displaystring | enumid
-------------+-----------+--------------------+---------------+--------
           0 |         1 | scmlin46 |               |
(1 row)

mydb=#


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> I tried to use "left join" to select data from my
> database. Result is come out, but I didn't see the
> value of "displayString". I added "left outer join",
> same result.

sounds like deeviceTypesEnum.enumID don't correspond to
devices.productType.

Jo

>
> SELECT   devices.ProductType,  devices.deviceKey,
> devices.fullDNSName, deviceTypesEnum.displayString,
> deviceTypesEnum.enumId FROM devices
>  LEFT JOIN deviceTypesEnum ON  deviceTypesEnum.enumId
> = devices.productType;
>
>
> Can anyone tell me how to modify this query?
>
> Thanks a lot!
>
> Zengfa
>
> [root@scmlin46 data]# psql -Umxadmin mydb_v1_0;
> Welcome to psql 7.3.2, the PostgreSQL interactive
> terminal.
>
> Type:  \copyright for distribution terms
>        \h for help with SQL commands
>        \? for help on internal slash commands
>        \g or terminate with semicolon to execute query
>        \q to quit
>
> mydb=# SELECT   devices.ProductType,
> devices.deviceKey, devices.fullDNSName,
> deviceTypesEnum.displayString, deviceTypesEnum.enumId
> FROM devices
> mysql=#  LEFT JOIN deviceTypesEnum ON
> deviceTypesEnum.enumId = devices.productType;
>  producttype | devicekey |    fulldnsname     |
> displaystring | enumid
> -------------+-----------+--------------------+---------------+--------
>            0 |         1 | scmlin46 |               |
> (1 row)
>
> mydb=#
>
>
> __________________________________
> Do you Yahoo!?
> Yahoo! SiteBuilder - Free, easy-to-use web site design software
> http://sitebuilder.yahoo.com
>
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