forked from rosh/MQL5Book
75 lines
2.7 KiB
MQL5
75 lines
2.7 KiB
MQL5
//+------------------------------------------------------------------+
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//| DBcreateTableFromStruct.mq5 |
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//| Copyright 2022, MetaQuotes Ltd. |
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//| https://www.mql5.com |
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//+------------------------------------------------------------------+
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#property description "Creates a table based on struct declaration. If the database doesn't exist, it creates it beforehand."
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#property script_show_inputs
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#include "..\..\Include\DBSQLite.mqh"
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#include "..\..\Include\TypeName.mqh"
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input string Database = "MQL5Book/DB/Example1";
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//+------------------------------------------------------------------+
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//| Example struct with common field types |
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//+------------------------------------------------------------------+
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struct Struct
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{
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long id;
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string name;
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double income;
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datetime time;
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};
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// Unfortunately we can't declare the fields once (inside the struct)
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// because every macro (see below) creates a templated struct underneath,
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// which is, because of nesting, makes the holding struct
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// complex and incompatible with DB-binding.
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// NB: if PRIMARY_KEY constaint is not specified for one of integer fields,
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// implicit 'rowid' column will be added as primary key automatically by SQL
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DB_FIELD_C1(Struct, long, id, DB_CONSTRAINT::PRIMARY_KEY);
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DB_FIELD(Struct, string, name);
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DB_FIELD(Struct, double, income);
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DB_FIELD(Struct, string, time);
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//+------------------------------------------------------------------+
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//| Script program start function |
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//+------------------------------------------------------------------+
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void OnStart()
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{
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DBSQLite db(Database);
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if(db.isOpen())
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{
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PRTF(db.createTable<Struct>());
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// the following modification will not throw error
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// on attempt of creating already existing table
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// PRTF(db.createTable<Struct>(true));
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PRTF(db.hasTable(TYPENAME(Struct)));
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}
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}
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//+------------------------------------------------------------------+
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/*
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1-st run with default inputs
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sql=CREATE TABLE Struct (id INTEGER PRIMARY KEY,
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name TEXT ,
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income REAL ,
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time TEXT ); / ok
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db.createTable<Struct>()=true / ok
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db.hasTable(typename(Struct))=true / ok
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2-nd run with default inputs
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sql=CREATE TABLE Struct (id INTEGER PRIMARY KEY,
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name TEXT ,
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income REAL ,
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time TEXT ); / ok
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database error, table Struct already exists
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db.createTable<Struct>()=false / DATABASE_ERROR(5601)
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db.hasTable(typename(Struct))=true / ok
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*/
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//+------------------------------------------------------------------+
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