61 lines
2.5 KiB
Markdown
61 lines
2.5 KiB
Markdown
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# DatabaseOpen
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Opens or creates a database in a specified file.
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```
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int DatabaseOpen(
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string filename, // file name
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uint flags // combination of flags
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);
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```
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Parameters
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filename
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[in] File name relative to the "MQL5\Files" folder.
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flags
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[in] Combination of flags from the [ENUM_DATABASE_OPEN_FLAGS](/en/docs/database/databaseopen#enum_database_open_flags) enumeration.
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Return Value
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If executed successfully, the function returns the database handle, which is then used to access the database. Otherwise, it returns [INVALID_HANDLE](/en/docs/constants/namedconstants/otherconstants). To get the error code, use GetLastError(), the possible responses are:
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- ERR_INTERNAL_ERROR (4001) – critical runtime error;
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- ERR_WRONG_INTERNAL_PARAMETER (4002) - internal error, while accessing the "MQL5\Files" folder;
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- ERR_INVALID_PARAMETER (4003) – path to the database file contains an empty string, or an incompatible combination of flags is set;
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- ERR_NOT_ENOUGH_MEMORY (4004) - insufficient memory;
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- ERR_WRONG_FILENAME (5002) - wrong database file name;
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- ERR_TOO_LONG_FILENAME (5003) - absolute path to the database file exceeds the maximum length;
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- ERR_DATABASE_TOO_MANY_OBJECTS (5122) - exceeded the maximum acceptable number of Database objects;
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- ERR_DATABASE_CONNECT (5123) - database connection error;
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- ERR_DATABASE_MISUSE (5621) - incorrect use of the SQLite library.
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Note
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If the filename parameter features NULL or the empty string "", a temporary file is created on the disk. It is automatically deleted after closing the database connection.
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If the filename parameter features ":memory:", the database is created in the memory and is automatically deleted after the connection to it is closed.
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If the flags parameter features none of the DATABASE_OPEN_READONLY or DATABASE_OPEN_READWRITE flags, the DATABASE_OPEN_READWRITE flag is used.
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If the file extension is not specified, ".sqlite" is used.
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ENUM_DATABASE_OPEN_FLAGS
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| ID | Description |
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| --- | --- |
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| DATABASE_OPEN_READONLY | Read only |
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| DATABASE_OPEN_READWRITE | Open for reading and writing |
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| DATABASE_OPEN_CREATE | Create the file on a disk if necessary |
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| DATABASE_OPEN_MEMORY | Create a database in RAM |
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| DATABASE_OPEN_COMMON | The file is in the common folder of all terminals |
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See also
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[DatabaseClose](/en/docs/database/databaseclose)
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