# src/db_connector/db_odbc

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Note: In order to use this module, run `nimble install db_connector`.

A higher level `ODBC` database wrapper.

This is the same interface that is implemented for other databases.

This has NOT yet been (extensively) tested against ODBC drivers for Teradata, Oracle, Sybase, MSSqlvSvr, et. al. databases.

Currently all queries are ANSI calls, not Unicode.

See also: db_postgres, db_sqlite, db_mysql.

# Parameter substitution

All `db_*` modules support the same form of parameter substitution. That is, using the `?` (question mark) to signify the place where a value should be placed. For example:

    sql"INSERT INTO myTable (colA, colB, colC) VALUES (?, ?, ?)"

# Examples

## Opening a connection to a database

    import db_connector/db_odbc
    var db = open("localhost", "user", "password", "dbname")
    db.close()

## Creating a table

    db.exec(sql"DROP TABLE IF EXISTS myTable")
    db.exec(sql("""CREATE TABLE myTable (
                     id integer,
                     name varchar(50) not null)"""))

## Inserting data

    db.exec(sql"INSERT INTO myTable (id, name) VALUES (0, ?)",
            "Andreas")

## Large example

    import db_connector/db_odbc
    import std/math

    var theDb = open("localhost", "nim", "nim", "test")

    theDb.exec(sql"Drop table if exists myTestTbl")
    theDb.exec(sql("create table myTestTbl (" &
        " Id    INT(11)     NOT NULL AUTO_INCREMENT PRIMARY KEY, " &
        " Name  VARCHAR(50) NOT NULL, " &
        " i     INT(11), " &
        " f     DECIMAL(18,10))"))

    theDb.exec(sql"START TRANSACTION")
    for i in 1..1000:
      theDb.exec(sql"INSERT INTO myTestTbl (name,i,f) VALUES (?,?,?)",
            "Item#" & $i, i, sqrt(i.float))
    theDb.exec(sql"COMMIT")

    for x in theDb.fastRows(sql"select * from myTestTbl"):
      echo x

    let id = theDb.tryInsertId(sql"INSERT INTO myTestTbl (name,i,f) VALUES (?,?,?)",
            "Item#1001", 1001, sqrt(1001.0))
    echo "Inserted item: ", theDb.getValue(sql"SELECT name FROM myTestTbl WHERE id=?", id)

    theDb.close()

# Imports

odbcsql, db_common, dbutils

# Types

    DbConn = OdbcConnTyp

  encapsulates a database connection

    InstantRow = tuple[row: seq[string], len: int]

  a handle that can be used to get a row's column text on demand

    Row = seq[string]

  a row of a dataset. NULL database values will be converted to nil.

# Procs

    proc `[]`(row: InstantRow; col: int): string {.inline, ...raises: [], tags: [],
        forbids: [].}

  Returns text for given column of the row

    proc close(db: var DbConn) {....tags: [WriteDbEffect], raises: [], forbids: [].}

  Closes the database connection.

    proc dbError(db: var DbConn) {....tags: [ReadDbEffect, WriteDbEffect],
                                   raises: [DbError], forbids: [].}

  Raises an `[DbError]` exception with ODBC error information

    proc dbQuote(s: string): string {.noSideEffect, ...raises: [], tags: [],
                                      forbids: [].}

  DB quotes the string.

    proc exec(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]) {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Executes the query and raises EDB if not successful.

    proc execAffectedRows(db: var DbConn; query: SqlQuery;
                          args: varargs[string, `$`]): int64 {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Runs the query (typically "UPDATE") and returns the number of affected rows

    proc getAllRows(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): seq[
        Row] {....tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Executes the query and returns the whole result dataset.

    proc getRow(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): Row {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Retrieves a single row. If the query doesn't return any rows, this proc will return a Row with empty strings for each column.

    proc getValue(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): string {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [], forbids: [].}

  Executes the query and returns the first column of the first row of the result dataset. Returns "" if the dataset contains no rows or the database value is NULL.

    proc insert(db: var DbConn; query: SqlQuery; pkName: string;
                args: varargs[string, `$`]): int64 {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  same as insertId

    proc insertId(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): int64 {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Executes the query (typically "INSERT") and returns the generated ID for the row.

    proc len(row: InstantRow): int {.inline, ...raises: [], tags: [], forbids: [].}

  Returns number of columns in the row

    proc open(connection, user, password, database: string): DbConn {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Opens a database connection.

  Raises `EDb` if the connection could not be established.

  Currently the database parameter is ignored, but included to match `open()` in the other db_xxxxx library modules.

    proc setEncoding(connection: DbConn; encoding: string): bool {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Currently not implemented for ODBC.

  Sets the encoding of a database connection, returns true for success, false for failure. result = set_character_set(connection, encoding) == 0

    proc tryExec(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): bool {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [], forbids: [].}

  Tries to execute the query and returns true if successful, false otherwise.

    proc tryInsert(db: var DbConn; query: SqlQuery; pkName: string;
                   args: varargs[string, `$`]): int64 {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [], forbids: [].}

  same as tryInsertID

    proc tryInsertId(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): int64 {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [], forbids: [].}

  Executes the query (typically "INSERT") and returns the generated ID for the row or -1 in case of an error.

    proc unsafeColumnAt(row: InstantRow; index: int): cstring {.inline, ...raises: [],
        tags: [], forbids: [].}

  Return cstring of given column of the row

# Iterators

    iterator fastRows(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): Row {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Executes the query and iterates over the result dataset.

  This is very fast, but potentially dangerous. Use this iterator only if you require ALL the rows.

  Breaking the fastRows() iterator during a loop may cause a driver error for subsequent queries

  Rows are retrieved from the server at each iteration.

    iterator instantRows(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): InstantRow {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Same as fastRows but returns a handle that can be used to get column text on demand using `[]`. Returned handle is valid only within the iterator body.

    iterator rows(db: var DbConn; query: SqlQuery; args: varargs[string, `$`]): Row {.
        ...tags: [ReadDbEffect, WriteDbEffect], raises: [DbError], forbids: [].}

  Same as `fastRows`, but slower and safe.

  This retrieves ALL rows into memory before iterating through the rows. Large dataset queries will impact on memory usage.

# Exports

DbColumn, DbTypeKind, DbColumns, DbError, ReadDbEffect, SqlQuery, sql, dbError, DbEffect, DbType, WriteDbEffect