136 lines
5.2 KiB
Markdown
136 lines
5.2 KiB
Markdown
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# DatabaseImport
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Imports data from a file into a table.
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```
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long DatabaseImport(
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int database, // database handle received in DatabaseOpen
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const string table, // name of a table to insert data
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const string filename, // name of a file to import data
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uint flags, // combination of flags
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const string separator, // data separator
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ulong skip_rows, // how many initial strings to skip
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const string skip_comments // string of characters defining comments
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);
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```
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Parameters
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database
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[in] Database handle received in [DatabaseOpen()](/en/docs/database/databaseopen).
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table
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[in] Name of a table the data from a file is to be added to.
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filename
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[in] CSV file or ZIP archive for reading data. The name may contain subdirectories and is set relative to the MQL5\Files folder.
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flags
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[in] Combination of flags from the [ENUM_DATABASE_IMPORT_FLAGS](/en/docs/database/databaseimport#enum_database_import_flags) enumeration.
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separator
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[in] Data separator in CSV file.
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skip_rows
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[in] Number of initial strings to be skipped when reading data from the file.
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skip_comments
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[in] String of characters for designating strings as comments. If any character from skip_comments is detected at the beginning of a string, such a string is considered a comment and is not imported.
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Return Value
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Return the number of imported strings or -1 in case of an error. To get the error code, use [GetLastError()](/en/docs/check/getlasterror), the possible responses are:
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- ERR_INVALID_PARAMETER (4003) – no table name specified (empty string or NULL);
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- ERR_DATABASE_INTERNAL (5120) – internal database error;
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- ERR_DATABASE_INVALID_HANDLE (5121) - invalid database handle.
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Note
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If there is no table named table, it is generated automatically. Names and field types in the created table are defined automatically based on the file data.
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If there is no table named table, it is generated automatically. Names and field types in the created table are defined automatically based on the file data.
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ENUM_DATABASE_IMPORT_FLAGS
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| ID | Description |
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| --- | --- |
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| DATABASE_IMPORT_HEADER | The first line contains the names of the table fields |
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| DATABASE_IMPORT_CRLF | CRLF (the default is LF) is considered a string break |
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| DATABASE_IMPORT_APPEND | Add data to the end of an existing table |
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| DATABASE_IMPORT_QUOTED_STRINGS | String values enclosed in double quotes |
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| DATABASE_IMPORT_COMMON_FOLDER | The file is stored in the common folder of all client terminals \Terminal\Common\File. |
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Example of reading the table from the file created by the code from the [DatabaseExport](/en/docs/database/databaseexport) example:
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```
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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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string csv_filename;
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//--- get the names of text files for downloading from the common folder of the client terminals
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string filenames[];
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if(FileSelectDialog("Select a CSV file to download a table", NULL,
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"Text files (*.csv)|*.csv",
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FSD_WRITE_FILE|FSD_COMMON_FOLDER, filenames, "data.csv")>0)
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{
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//--- display the name of each selected file
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if(ArraySize(filenames)==1)
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csv_filename=filenames[0];
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else
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{
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Print("Unknown error while selecting file. Error code ", GetLastError());
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return;
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}
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}
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else
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{
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Print("CSV file not selected");
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return;
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}
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//--- create or open a database
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string db_filename="test.sqlite";
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int db=DatabaseOpen(db_filename, DATABASE_OPEN_READWRITE|DATABASE_OPEN_CREATE);
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//--- check if the TEST table exists
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if(DatabaseTableExists(db, "TEST"))
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{
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//--- remove the TEST table
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if(!DatabaseExecute(db, "DROP TABLE IF EXISTS TEST"))
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{
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Print("Failed to drop the TEST table with code ", GetLastError());
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DatabaseClose(db);
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return;
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}
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}
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//--- import entries from the file to the TEST table
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long imported=DatabaseImport(db, "TEST", csv_filename, DATABASE_IMPORT_HEADER|DATABASE_IMPORT_COMMON_FOLDER|DATABASE_IMPORT_APPEND, ";", 0, NULL);
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if(imported>0)
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{
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Print(imported," lines imported in table TEST");
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DatabasePrint(db,"SELECT * FROM TEST",DATABASE_PRINT_NO_INDEX);
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}
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else
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{
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Print("DatabaseImport() failed. Error ",GetLastError());
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}
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//--- close the database file and inform of that
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DatabaseClose(db);
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PrintFormat("Database: %s closed", db_filename);
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}
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```
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See also
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[DatabaseOpen](/en/docs/database/databaseopen), [DatabasePrint](/en/docs/database/databaseprint)
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