NAME
    PApp::SQL - absolutely easy yet fast and powerful sql access.

SYNOPSIS
     use PApp::SQL;

     my $st = sql_exec $DBH, "select ... where a = ?", $a;

     local $DBH = <database handle>;
     my $st = sql_exec \my($bind_a, $bind_b), "select a,b ...";
     my $id = sql_insertid
                 sql_exec "insert into ... values (?, ?)", $v1, $v2;
     my $a = sql_fetch "select a from ...";
     sql_fetch \my($a, $b), "select a,b ...";

     sql_exists "table where name like 'a%'"
        or die "a* required but not existent";

     my $db = new PApp::SQL::Database "", "DBI:mysql:test", "user", "pass";
     local $PApp::SQL::DBH = $db->checked_dbh; # does 'ping'

     sql_exec $db->dbh, "select ...";

DESCRIPTION
    This module provides you with easy-to-use functions to execute sql
    commands (using DBI). Despite being easy to use, they are also quite
    efficient and allow you to write faster programs in fewer lines of code.
    It should work with anything from perl-5.004_01 onwards, but I only
    support 5.005+. UTF8 handling (the "sql_u*" family of functions) will
    only be effective with perl version 5.006 and beyond.

    If the descriptions here seem terse or if you always wanted to know what
    PApp is then have a look at the PApp module which uses this module
    extensively but also provides you with a lot more gimmicks to play
    around with to help you create cool applications ;)

  Global Variables
    $sql_exec
        Since the "sql_exec" family of functions return a statement handle
        there must be another way to test the return value of the "execute"
        call. This global variable contains the result of the most recent
        call to "execute" done by this module.

    $PApp::SQL::DBH
        The default database handle used by this module if no $DBH was
        specified as argument. See "sql_exec" for a discussion.

    $PApp::SQL::Database
        The current default "PApp::SQL::Database"-object. Future versions
        might automatically fall back on this database and create database
        handles from it if neccessary. At the moment this is not used by
        this module but might be nice as a placeholder for the database
        object that corresponds to $PApp::SQL::DBH.

  Functions
    $dbh = connect_cached $id, $dsn, $user, $pass, $flags, $connect
        (not exported by by default)

        Connect to the database given by "($dsn,$user,$pass)", while using
        the flags from $flags. These are just the same arguments as given to
        "DBI->connect".

        The database handle will be cached under the unique id
        "$id|$dsn|$user|$pass". If the same id is requested later, the
        cached handle will be checked (using ping), and the connection will
        be re-established if necessary (be sure to prefix your application
        or module name to the id to make it "more" unique. Things like
        __PACKAGE__ . __LINE__ work fine as well).

        The reason $id is necessary is that you might specify special
        connect arguments or special flags, or you might want to configure
        your $DBH differently than maybe other applications requesting the
        same database connection. If none of this is necessary for your
        application you can leave $id empty (i.e. "").

        If specified, $connect is a callback (e.g. a coderef) that will be
        called each time a new connection is being established, with the new
        $dbh as first argument.

        Examples:

         # try your luck opening the papp database without access info
         $dbh = connect_cached __FILE__, "DBI:mysql:papp";

        Mysql-specific behaviour: The default setting of
        "mysql_client_found_rows" is TRUE, you can overwrite this, though.

    $sth = sql_exec [dbh,] [bind-vals...,] "sql-statement", [arguments...]
    $sth = sql_uexec <see sql_exec>
        "sql_exec" is the most important and most-used function in this
        module.

        Runs the given sql command with the given parameters and returns the
        statement handle. The command and the statement handle will be
        cached (with the database handle and the sql string as key), so
        prepare will be called only once for each distinct sql call (please
        keep in mind that the returned statement will always be the same,
        so, if you call "sql_exec" with the same dbh and sql-statement twice
        (e.g. in a subroutine you called), the statement handle for the
        first call mustn't not be in use anymore, as the subsequent call
        will re-use the handle.

        The database handle (the first argument) is optional. If it is
        missing, it tries to use database handle in $PApp::SQL::DBH, which
        you can set before calling these functions. NOTICE: future and
        former versions of PApp::SQL might also look up the global variable
        $DBH in the callers package.

        The actual return value from the "$sth->execute" call is stored in
        the package-global (and exported) variable $sql_exec.

        If any error occurs "sql_exec" will throw an exception.

        "sql_uexec" is similar to "sql_exec" but upgrades all input
        arguments to UTF-8 before calling the "execute" method.

        Examples:

         # easy one
         my $st = sql_exec "select name, id from table where id = ?", $id;
         while (my ($name, $id) = $st->fetchrow_array) { ... };

         # the fastest way to use dbi, using bind_columns
         my $st = sql_exec \my($name, $id),
                           "select name, id from table where id = ?",
                           $id;
         while ($st->fetch) { ...}

         # now use a different dastabase:
         sql_exec $dbh, "update file set name = ?", "oops.txt";

    sql_fetch <see sql_exec>
    sql_ufetch <see sql_uexec>
        Execute an sql-statement and fetch the first row of results.
        Depending on the caller context the row will be returned as a list
        (array context), or just the first columns. In table form:

         CONTEXT        RESULT
         void           ()
         scalar         first column
         list           array

        "sql_fetch" is quite efficient in conjunction with bind variables:

         sql_fetch \my($name, $amount),
                   "select name, amount from table where id name  = ?",
                   "Toytest";

        But of course the normal way to call it is simply:

         my($name, $amount) = sql_fetch "select ...", args...

        ... and it's still quite fast unless you fetch large amounts of
        data.

        "sql_ufetch" is similar to "sql_fetch" but upgrades all input values
        to UTF-8 and forces all result values to UTF-8 (this does *not*
        include result parameters, only return values. Using bind variables
        in conjunction with sql_u* functions might result in undefined
        behaviour - we use UTF-8 on bind-variables at execution time and it
        seems to work on DBD::mysql as it ignores the UTF-8 bit completely.
        Which just means that that DBD-driver is broken).

    sql_fetchall <see sql_exec>
    sql_ufetchall <see sql_uexec>
        Similarly to "sql_fetch", but all result rows will be fetched (this
        is of course inefficient for large results!). The context is ignored
        (only list context makes sense), but the result still depends on the
        number of columns in the result:

         COLUMNS        RESULT
         0              ()
         1              (row1, row2, row3...)
         many           ([row1], [row2], [row3]...)

        Examples (all of which are inefficient):

         for (sql_fetchall "select id from table") { ... }

         my @names = sql_fetchall "select name from user";

         for (sql_fetchall "select name, age, place from user") {
            my ($name, $age, $place) = @$_;
         }

        "sql_ufetchall" is similar to "sql_fetchall" but upgrades all input
        values to UTF-8 and forces all result values to UTF-8 (see the
        caveats in the description of "sql_ufetch", though).

    sql_exists "<table_references> where <where_condition>...", args...
    sql_uexists <see sql_exists>
        Check wether the result of the sql-statement "select xxx from
        $first_argument" would be empty or not (that is, imagine the string
        "select * from" were prepended to your statement (it isn't)). Should
        work with every database but can be quite slow, except on mysql,
        where this should be quite fast.

        "sql_uexists" is similar to "sql_exists" but upgrades all parameters
        to UTF-8.

        Examples:

         print "user 7 exists!\n"
            if sql_exists "user where id = ?", 7;
 
         die "duplicate key"
            if sql_exists "user where name = ? and pass = ?", "stefan", "geheim";

    $lastid = sql_insertid $sth
        Returns the last automatically created key value. It must be
        executed directly after executing the insert statement that created
        it. This is what is actually returned for various databases. If your
        database is missing, please send me an e-mail on how to implement
        this ;)

         mariadb:  first C<AUTO_INCREMENT> column set to NULL
         mysql:    first C<AUTO_INCREMENT> column set to NULL
         postgres: C<oid> column (is there a way to get the last SERIAL?)
         sybase:   C<IDENTITY> column of the last insert (slow)
         informix: C<SERIAL> or C<SERIAL8> column of the last insert
         sqlite:   C<last_insert_rowid()>

        Except for sybase, this does not require a server access.

    [old-size] = cachesize [new-size]
        Returns (and possibly changes) the LRU cache size used by
        "sql_exec". The default is somewhere around 50 (= the 50 last
        recently used statements will be cached). It shouldn't be too large,
        since a simple linear list is used for the cache at the moment
        (which, for small (<100) cache sizes is actually quite fast).

        The function always returns the cache size in effect *before* the
        call, so, to nuke the cache (for example, when a database connection
        has died or you want to garbage collect old database/statement
        handles), this construct can be used:

         PApp::SQL::cachesize PApp::SQL::cachesize 0;

    reinitialize [not exported]
        Clears any internal caches (statement cache, database handle cache).
        Should be called after "fork" and other accidents that invalidate
        database handles.

  Type Deduction
    Since every database driver seems to deduce parameter types differently,
    usually wrongly, and at leats in the case of DBD::mysql, different in
    every other release or so, and this can and does lead to data
    corruption, this module does type deduction itself.

    What does it mean? Simple - sql parameters for placeholders will be
    explicitly marked as SQL_VARCHAR, SQL_INTEGER or SQL_DOUBLE the first
    time a statement is prepared.

    To force a specific type, you can either continue to use e.g. sql casts,
    or you can make sure to consistently use strings or numbers. To make a
    perl scalar look enough like a string or a number, use this when passing
    it to sql_exec or a similar functions:

       "$string"   # to pass a string
       $num+0      # to pass a number

  The Database Class
    Again (sigh) the problem of persistency. What do you do when you have to
    serialize on object that contains (or should contain) a database handle?
    Short answer: you don't. Long answer: you can embed the necessary
    information to recreate the dbh when needed.

    The "PApp::SQL::Database" class does that, in a relatively efficient
    fashion: the overhead is currently a single method call per access (you
    can cache the real dbh if you want).

    $db = new <same arguments as "connect_cached">
        The "new" call takes the same arguments as "connect_cached"
        (obviously, if you supply a connect callback it better is
        serializable, see PApp::Callback!) and returns a serializable
        database class. No database handle is actually being created.

    $db->dbh
        Return the database handle as fast as possible (usually just a hash
        lookup).

    $db->checked_dbh
        Return the database handle, but first check that the database is
        still available and re-open the connection if necessary.

    $db->dsn
        Return the DSN (DBI) fo the database object (e.g. for error
        messages).

    $db->login
        Return the login name.

    $db->password
        Return the password (emphasizing the fact that the password is
        stored plaintext ;)

SEE ALSO
    PApp.

AUTHOR
     Marc Lehmann <schmorp@schmorp.de>
     http://home.schmorp.de/