Re: PostgreSQL add id column that increments based on data

On 08/01/2014 02:15 AM, DerekW wrote:
> I am relatively new to using Postgres, coming from a MySQL background. I am
> using Postgres 9.3.4 on Windows x64.
>
> We are being supplied data in multiple fixed length text files. The first
> digit on each line is a number between 1 and 4 that indicates the record
> type of the data in that row. The rows are grouped sequentially such that
> there will always first be a row of type 1 followed by zero or more rows of
> the other types.
>
>      data_x.txt
>      ---------------------
>      1data01
>      2data02
>      4data03
>      4data04
>      1data05
>      1data06
>      3data07
>
> To import this into Postgres I have used the following SQL commands:
>
>      CREATE TABLE data_raw (
>          raw_data TEXT
>      );
>
>      COPY data_raw FROM 'C:\path\data_x.txt' ...; -- Repeated for each file
>
>      ALTER TABLE data_raw
>          ADD COLUMN indicator integer;
>
>      UPDATE data_raw SET
>          indicator = CAST(substr(raw_data, 1, 1) AS integer),
>          raw_data = substr(raw_data, 2);
>
> I then create tables for each of the 4 record types:
>
>      CREATE TABLE table_1 SELECT raw_data FROM data_raw WHERE indicator = 1;
>      CREATE TABLE table_2 SELECT raw_data FROM data_raw WHERE indicator = 2;
>      CREATE TABLE table_3 SELECT raw_data FROM data_raw WHERE indicator = 3;
>      CREATE TABLE table_4 SELECT raw_data FROM data_raw WHERE indicator = 4;
>
> What I need to do, but am unsure how, is to also add an "id" column for each
> group where the indicator starts with 1. We will be getting weekly updates
> so I need to specify the initial id for each batch. So if this batch starts
> at id = 225, then I want to get the following tables from the sample data:
>
>      table_1
>      id  | raw_data
>      --------------------
>      225 | data01
>      226 | data05
>      227 | data06
>
>      table_2
>      id  | raw_data
>      --------------------
>      225 | data02
>
>      table_3
>      id  | raw_data
>      --------------------
>      227 | data07
>
>      table_4
>      id  | raw_data
>      --------------------
>      225 | data03
>      225 | data04

I am not following the logic of the id numbering scheme. I see the 
sequential numbering for indicator 1. Not why indicator 2 uses 225 again 
when indicator 3 starts with 227 and indicator 4 has the same id for 
both rows. My guess, whatever the logic is, it is going to involve 
triggers and possibly another table to keep track of batch numbers

>
>
>
>
>
>
> --
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http://postgresql.1045698.n5.nabble.com/PostgreSQL-add-id-column-that-increments-based-on-data-tp5813514.html
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>
>


-- 
Adrian Klaver
adrian.klaver@aklaver.com