PureBasic Forums - English

Posted: **Tue Mar 12, 2019 1:56 pm**

Is there a plan to support indexed files? Sometimes it would be easier to use an indexed file instead of a database. For example if I only need one (or relatively small number of files) indexed file. I think that working with the database can also be very hard if you don't have enough experience. Indexed files are very easy to use.

More info could be provided if required. Some info is here:

https://documentation.microfocus.com/he ... _4_7_1_1_3

Other file organizations: https://documentation.microfocus.com/he ... _7_4_7_1_1

There are two ways how to handle indexes:
1. one is to store this information in the .dat file itself
2. the other is to have two separate files: .dat and .idx

Saso

Posted: **Tue Mar 12, 2019 3:40 pm**

For a small amount of data, you could use a structure with fixed length strings.

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Structure Record
  MembershipNumber.w
  Name.s{20}
EndStructure

Dim Records.Record(99)

With Records(0)
  \MembershipNumber = 1000
  \Name = "John"
EndWith

With Records(99)
  \MembershipNumber = 1100
  \Name = "Luke"
EndWith

If CreateFile(0, "SimpleDatabase.dat")
  WriteData(0, @Records(), 100 * SizeOf(Record))
  CloseFile(0)
EndIf

In this case it's very easy to read or write an entire array.
If you are working with a file instead of an array, it's also easy to seek a record by changing the file pointer.

Posted: **Tue Mar 12, 2019 4:12 pm**

miskox wrote:...working with the database can also be very hard...

Quite simple, actually. Here are the component functions, broken down for clarity.

1. Creating an empty SQLite database file (first time only):

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CreateFile(0, GetTemporaryDirectory() + "myDB.sqlite")
CloseFile(0)

2. Preparing the "structure" of the SQLite database (first time only):

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UseSQLiteDatabase()

OpenDatabase(0, GetTemporaryDirectory() + "myDB.sqlite", "", "")
DatabaseUpdate(0, "CREATE TABLE indexFile (name CHAR(200), age INT)")
CloseDatabase(0)

3. Writing data to the SQLite database:

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UseSQLiteDatabase()

OpenDatabase(0, GetTemporaryDirectory() + "myDB.sqlite", "", "")
DatabaseUpdate(0, "INSERT INTO indexFile (name, age) VALUES ('Einstein', '76')")
DatabaseUpdate(0, "INSERT INTO indexFile (name, age) VALUES ('DaVinci', '67')")
DatabaseUpdate(0, "INSERT INTO indexFile (name, age) VALUES ('Newton', '84')")
CloseDatabase(0)

4. Updating data in the SQLite database:

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UseSQLiteDatabase()

OpenDatabase(0, GetTemporaryDirectory() + "myDB.sqlite", "", "")
DatabaseUpdate(0, "UPDATE indexFile SET name='Isaac Newton' WHERE name='Newton'")
CloseDatabase(0)

5. Reading data from the SQLite database:

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UseSQLiteDatabase()

OpenDatabase(0, GetTemporaryDirectory() + "myDB.sqlite", "", "")
DatabaseQuery(0, "SELECT * from indexFile WHERE name='Isaac Newton'")
While NextDatabaseRow(0)
  age = GetDatabaseLong(0, 1)
Wend
Debug "Isaac Newton was " + Str(age) + " years old."
CloseDatabase(0)

That's all that's really required to use an SQLite database!

Posted: **Thu Mar 14, 2019 10:52 am**

Or the easy-json way

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Structure strDaten
	name.s
	id.d
EndStructure

Structure strD
	List daten.strDaten()
EndStructure

Procedure saveData(file.s,*d.strD)
	Protected json=CreateJSON(#PB_Any)
	InsertJSONStructure(JSONValue(json),*d,strD)
	SaveJSON(json,file)
	FreeJSON(json)
EndProcedure

Procedure loadData(file.s)
	Protected *d.strD=AllocateStructure(strD)
	Protected json=LoadJSON(#PB_Any,file)
	ExtractJSONStructure(JSONValue(json),*d,strD)
	FreeJSON(json)
	ProcedureReturn *d
EndProcedure

Testing

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Protected *d.strD=AllocateStructure(strD)
AddElement(*d\daten())
*d\daten()\id=1
*d\daten()\name="Test 1"

AddElement(*d\daten())
*d\daten()\id=2
*d\daten()\name="Test 2"

saveData("Daten.json",*d)

Protected *d2.strD=loadData("Daten.json")
ForEach *d2\daten()
	Debug *d2\daten()\name
Next

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Indexed files

Indexed files

Re: Indexed files

Re: Indexed files

Re: Indexed files