# std/db_mysql

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A higher level mySQL database wrapper. The same interface is implemented for other databases too.

See also: db_odbc, db_sqlite, db_postgres.

# 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 std/db_mysql
    let 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, ?)",
            "Dominik")

## Larger example

    import std/[db_mysql, math]

    let 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

strutils, mysql, db_common, since

# Types

    DbConn = distinct PMySQL

  encapsulates a database connection Source Edit

    InstantRow = object
      row: cstringArray
      len: int

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

    Row = seq[string]

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

# Procs

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

  Returns text for given column of the row. Source Edit

    proc close(db: DbConn) {....tags: [DbEffect], raises: [].}

  closes the database connection. Source Edit

    proc dbError(db: DbConn) {.noreturn, ...raises: [DbError], tags: [].}

  raises a DbError exception. Source Edit

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

  DB quotes the string. Note that this doesn't escape `%` and `_`. Source Edit

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

  executes the query and raises EDB if not successful. Source Edit

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

  runs the query (typically "UPDATE") and returns the number of affected rows Source Edit

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

  executes the query and returns the whole result dataset. Source Edit

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

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

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

  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. Source Edit

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

  same as insertId Source Edit

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

  executes the query (typically "INSERT") and returns the generated ID for the row. Source Edit

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

  Returns number of columns in the row. Source Edit

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

  opens a database connection. Raises `EDb` if the connection could not be established. Source Edit

    proc setEncoding(connection: DbConn; encoding: string): bool {....tags: [DbEffect],
        raises: [].}

  sets the encoding of a database connection, returns true for success, false for failure. Source Edit

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

  tries to execute the query and returns true if successful, false otherwise. Source Edit

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

  same as tryInsertID Source Edit

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

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

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

  Return cstring of given column of the row Source Edit

# Iterators

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

  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 will cause the next database query to raise an [EDb] exception `Commands out of sync`.

  Source Edit

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

  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. Source Edit

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

  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. Source Edit

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

  same as `fastRows`, but slower and safe. Source Edit

# Exports

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