Home/ Questions/Q 6969089
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-27T16:32:12+00:00

I have a text file that I parse each month and insert the data

  • 0

I have a text file that I parse each month and insert the data into my database. The text file looks like this.

------------------------------------------------------------------------------------------------------------------------------------------------------------
BLK. NO 410              | 1   2|  3   4   5   6   7 | 8   9| 10  11  12  13  14 |15  16| 17  18  19  20  21 |22  23| 24  25  26  27  28 |29  30| 31   1   2
          BLK   88.35    |SA  SU| MO  TU  WE  TH  FR |SA  SU| MO  TU  WE  TH  FR |SA  SU| MO  TU  WE  TH  FR |SA  SU| MO  TU  WE  TH  FR |SA  SU| MO  TU  WE
          CR.   88.35           |194   / 159         |      |194   / 159         |      |194   / 159         |      |194   / 159         |      |239        
          OFF      14      :   : VER DFW TRC DFW   X   :   : VER DFW TRC DFW   X   :   : VER DFW TRC DFW   X   :   : VER DFW TRC DFW   X   :   : CUU DFW    
C/O 06.00 TAFB 216.15   194=/1410/1055/0740, 159=/0900/1700/1400, 239=/1845/1945/0155
EM3 25.55 ERD 42.00 EM4 20.40 
-----------------------------------------------------------------------------------------------------------------------------

This text file has from 100 to 300 of these records (we refer to it as a “line of flying”) and I use it to determine my flight schedule each month. I am parsing this file just fine but the company added a new wrinkle.

This “line” can be for a pilot or a flight attendant. Until recently each line could be for a captain or First Officer. But now some files have captain lines and first officer lines. The flight attendant file could have 1 or two flight attendant positions or more depending on the type of aircraft flown.

I need to create a new column in my database that reflects this new information. Once the lines are saved to the database, they are only searched, never updated again. I don’t want to add a new table just to keep track of this information. I want to add a new column to the existing table. Here is my strategy.

When I parse the text file, I will keep track of the positions available. If it is for Captain, I will save “CA” to the database. If it is first officer, I will save “FO”. If it is for both a captain and First officer, I will save “CAFO”. For flight attendants I will save a number “1” for 1 flight attendant poistion. For each additional poistion, I will just increment it one number. This would allow for expansion later if larger aiplanes required more flight attendant poistions.

So to recap, I will save one the following for each database record.

  • “CAFO”
  • “CA”
  • “FO”
  • “1”
  • “2”

Now I will need to access the database and retrieve these records for my web program. If a captain wants to retreive records He will want only captain lines which would be “CAFO” or “CA”. And just the opposite for first officers.
When I do the query, I found that I could use the mySQL command SUBSTRING to just grab the first 2 or last 2 characters.

for captain lines

SELECT Line_number,html_text FROM lines WHERE SUBSTRING(Crew_type,1,2)=”CA”

This would just get the first two beginning characters from the record and it would match both cases.
For First officers I start at the end of the string and grab last two characters.

SELECT Line_number,html_text FROM lines WHERE SUBSTRING(Crew_type,-2)=”FO”

For flight attendants I could compare the number.
If a flight attendant only wanted lines with 1 position.

SELECT Line_number,html_text FROM lines WHERE Crew_type = “1”

Or if they want all possible flight attendant positions

SELECT Line_number,html_text FROM lines WHERE Crew_type >= “1”

I would set the column type to ENUM with the values I listed above.

My question is there a better way to approach this problem? I will only be inserting once, but will be retreiving a lot. Will the SUBSTRING command slow down the queries too much?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team
    SELECT Line_number,html_text FROM lines WHERE SUBSTRING(Crew_type,1,2)="CA"

    will be a performance killer, as it calculates the substring for all records, not only those used. You want 

    SELECT Line_number,html_text FROM lines Crew_type in ("CA", "CAFO")

    Ditto for FO.

    So somewhere in your PHP iw would define

    $matches=array(
  'CA'=>'"CA","CAFO"',
  'FO'=>'"FO","CAFO"',
  'FA'=>'"1","2"'
);

    and then use 

    $match=$matches[$crew_type];
$sql="SELECT Line_number,html_text FROM lines Crew_type in ($match)";

    with $crew_type being one of ‘CA’,’FO’,’FA’

    • 0