Sophie: libdbi-devel-0.8.3-3mdv2010.0 i586

libdbi-devel-0.8.3-3mdv2010.0.i586.rpm

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>Database Independent Abstraction Layer for C: libdbi Programmer's Guide</TH
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>Chapter 2. libdbi in a Nutshell (Quickstart Guide)</TD
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><H1
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><A
NAME="QUICKSTART-DEBRIEFING"
>2.1. Quick Overview</A
></H1
><P
>      libdbi uses a plugin system that allows various databases to be supported simultaneously, and can dynamically load or unload drivers that are supplied by libdbi or a third party. The library is initiallized by calling <A
HREF="reference-core.html#DBI-INITIALIZE"
>dbi_initialize</A
> and a connection instance is started by calling either <A
HREF="reference-conn.html#DBI-CONN-NEW"
>dbi_conn_new</A
> or both <A
HREF="reference-driver.html#DBI-DRIVER-OPEN"
>dbi_driver_open</A
> and <A
HREF="reference-conn.html#DBI-CONN-OPEN"
>dbi_conn_open</A
>.
    </P
><P
>      The connection's options (username, password, hostname, etc.) are set with <A
HREF="reference-conn.html#DBI-CONN-SET-OPTION"
>dbi_conn_set_option</A
> and <A
HREF="reference-conn.html#DBI-CONN-SET-OPTION-NUMERIC"
>dbi_conn_set_option_numeric</A
>. Once all options are set, <A
HREF="reference-database.html#DBI-CONN-CONNECT"
>dbi_conn_connect</A
> will connect to the database, waiting to handle a <A
HREF="reference-query.html#DBI-CONN-QUERY"
>dbi_conn_query</A
>. A query is a string containing a valid SQL statement. libdbi provides several functions to automatically quote any characters that might screw up the query string. The preferred functions are <A
HREF="reference-query.html#DBI-CONN-QUOTE-STRING"
>dbi_conn_quote_string</A
> and <A
HREF="reference-query.html#DBI-CONN-QUOTE-STRING-COPY"
>dbi_conn_quote_string_copy</A
> as they take into consideration the character encoding used by the current connection. The legacy functions <A
HREF="reference-driver.html#DBI-DRIVER-QUOTE-STRING"
>dbi_driver_quote_string</A
> and <A
HREF="reference-driver.html#DBI-DRIVER-QUOTE-STRING-COPY"
>dbi_driver_quote_string_copy</A
> are still supported but should be avoided in new code. After a successful query, you can retrieve rows with <A
HREF="reference-results.html#DBI-RESULT-FIRST-ROW"
>dbi_result_first_row</A
>, <A
HREF="reference-results.html#DBI-RESULT-LAST-ROW"
>dbi_result_last_row</A
>, <A
HREF="reference-results.html#DBI-RESULT-PREV-ROW"
>dbi_result_prev_row</A
>, <A
HREF="reference-results.html#DBI-RESULT-NEXT-ROW"
>dbi_result_next_row</A
>, and <A
HREF="reference-results.html#DBI-RESULT-SEEK-ROW"
>dbi_result_seek_row</A
>.
    </P
><P
>String data may be sent to and retrieved from a database using character encodings if they contain characters not covered by the ASCII character set. Most database engines support character encodings like ISO-8859-1, suitable for many European languages, or even the multibyte Unicode character sets like UTF-8. The character set used to store your data in your database is usually set by the <B
CLASS="COMMAND"
>CREATE DATABASE</B
> command, which you have to take care of yourself. libdbi uses the connection option "encoding" to select a particular character encoding for the current connection. If you set the value to "auto", libdbi will automatically use the database character encoding as the connection encoding. If you request a different character encoding, as defined by its <A
HREF="http://www.iana.org"
TARGET="_top"
>IANA</A
> name, libdbi will convert the data on the fly.</P
><P
>      There are two methods for fetching field data, and two ways to perform each method. You can either "pull" the data from DBI using the <TT
CLASS="LITERAL"
>dbi_result_get_*</TT
> family of functions, or have DBI automatically "push" the data into predefined variables with the <TT
CLASS="LITERAL"
>dbi_result_bind_*</TT
> family of functions. Both families of functions are as strongly typed as most SQL database engines are. That is, you must use the <TT
CLASS="LITERAL"
>dbi_result_get_*</TT
> or <TT
CLASS="LITERAL"
>dbi_result_bind_*</TT
> function that matches the type of the requested field. <A
HREF="quickstart-debriefing.html#TABLE-GET-BIND-FUNCTIONS"
>Table 2-1</A
> shows an overview of these functions sorted by the field type they retrieve.
    </P
><P
>      Pulling the data from the database can be done with one of the "get" functions such as <A
HREF="reference-field.html#DBI-RESULT-GET-LONG"
>dbi_result_get_long</A
> or <A
HREF="reference-field.html#DBI-RESULT-GET-STRING"
>dbi_result_get_string</A
>, which simply return the data in the field you asked for. You should run the function <A
HREF="reference-conn.html#DBI-CONN-ERROR-FLAG"
>dbi_conn_error_flag</A
> immediately after each call to a "get" function to check for errors. You can also get more than one field at a time with <A
HREF="reference-field.html#DBI-RESULT-GET-FIELDS"
>dbi_result_get_fields</A
>, which uses a printf-like syntax.
    </P
><P
>      If you want DBI to automatically fill your program's variables with field values whenever a new row is fetched, you can "bind" fields to your variables. Bindings are set up with <A
HREF="reference-field.html#DBI-RESULT-BIND-LONG"
>dbi_result_bind_long</A
>, <A
HREF="reference-field.html#DBI-RESULT-BIND-STRING"
>dbi_result_bind_string</A
>, and the rest of the bind family of functions. Like the associated "get" function, you can set up multiple bindings at once with the <A
HREF="reference-field.html#DBI-RESULT-BIND-FIELDS"
>dbi_result_bind_fields</A
> function.
    </P
><P
>String data can be safely included into query strings by using the <A
HREF="reference-query.html#DBI-CONN-QUOTE-STRING"
>dbi_conn_quote_string</A
> and <A
HREF="reference-query.html#DBI-CONN-QUOTE-STRING-COPY"
>dbi_conn_quote_string_copy</A
> functions. Binary data can be included into query strings by using the <A
HREF="reference-query.html#DBI-CONN-QUOTE-BINARY-COPY"
>dbi_conn_quote_binary_copy</A
> function. All of these functions return zero-terminated strings enclosed in the appropriate quoting characters. Binary strings are returned in their binary representation. That is, they may contain null bytes and other non-printable characters. It is mandatory to use the <A
HREF="reference-field-meta.html#DBI-RESULT-GET-FIELD-LENGTH"
>dbi_result_get_field_length</A
> or <A
HREF="reference-field-meta.html#DBI-RESULT-GET-FIELD-LENGTH-IDX"
>dbi_result_get_field_length_idx</A
> functions to determine the number of bytes contained in the binary string.</P
><P
><EM
>Caveats:</EM
></P
><P
></P
><UL
><LI
><P
>For fields holding integers (not fractional numbers), DBI differentiates between signed and unsigned variables. By default, DBI returns signed values. If you want an unsigned value, prepend a "u" to the name of the target type. For example, dbi_result_bind_short becomes dbi_result_bind_ushort.</P
></LI
><LI
><P
>You must set up any bindings <EM
>after</EM
> a successful query but <EM
>before</EM
> you fetch any rows. Even if you are using field bindings, you can still use the dbi_result_get_* functions as usual. (actually, I lied... setting up a binding should theoretically work at any time, but don't plan on this behavior in future versions)</P
></LI
><LI
><P
>All string and binary data returned or bound from DBI is <EM
>read-only</EM
>. If you want your own local copy that can be modified at will, use <A
HREF="reference-field.html#DBI-RESULT-GET-STRING-COPY"
>dbi_result_get_string_copy</A
>, <A
HREF="reference-field.html#DBI-RESULT-GET-BINARY-COPY"
>dbi_result_get_binary_copy</A
>, <A
HREF="reference-field.html#DBI-RESULT-BIND-STRING-COPY"
>dbi_result_bind_string_copy</A
>, or <A
HREF="reference-field.html#DBI-RESULT-BIND-BINARY-COPY"
>dbi_result_bind_binary_copy</A
>. You will be responsible for freeing the memory allocated by these functions.</P
></LI
></UL
><P
>      <A
HREF="reference-results.html#DBI-RESULT-NEXT-ROW"
>dbi_result_next_row</A
> and the other row-seeking functions will return zero when there are no more rows available. Before the next database operation is performed, you must call <A
HREF="reference-results.html#DBI-RESULT-FREE"
>dbi_result_free</A
>.  Before the program terminates, the connection must be disconnected and unloaded with <A
HREF="reference-conn.html#DBI-CONN-CLOSE"
>dbi_conn_close</A
> and libdbi must be unloaded with <A
HREF="reference-core.html#DBI-SHUTDOWN"
>dbi_shutdown</A
>.
    </P
><DIV
CLASS="TABLE"
><A
NAME="TABLE-GET-BIND-FUNCTIONS"
></A
><P
><B
>Table 2-1. get* and bind* functions sorted by field type</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>field type</TH
><TH
>get by name</TH
><TH
>get by field index</TH
><TH
>bind</TH
></TR
></THEAD
><TBODY
><TR
><TD
>signed char</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-CHAR"
>dbi_result_get_char</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-CHAR-IDX"
>dbi_result_get_char_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-CHAR"
>dbi_result_bind_char</A
></TD
></TR
><TR
><TD
>unsigned char</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-UCHAR"
>dbi_result_get_uchar</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-UCHAR-IDX"
>dbi_result_get_uchar_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-UCHAR"
>dbi_result_bind_uchar</A
></TD
></TR
><TR
><TD
>short</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-SHORT"
>dbi_result_get_short</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-SHORT-IDX"
>dbi_result_get_short_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-SHORT"
>dbi_result_bind_short</A
></TD
></TR
><TR
><TD
>unsigned short</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-USHORT"
>dbi_result_get_ushort</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-USHORT-IDX"
>dbi_result_get_ushort_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-USHORT"
>dbi_result_bind_ushort</A
></TD
></TR
><TR
><TD
>int</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-INT"
>dbi_result_get_int</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-INT-IDX"
>dbi_result_get_int_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-INT"
>dbi_result_bind_int</A
></TD
></TR
><TR
><TD
>unsigned int</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-UINT"
>dbi_result_get_uint</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-UINT-IDX"
>dbi_result_get_uint_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-UINT"
>dbi_result_bind_uint</A
></TD
></TR
><TR
><TD
>long long</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-LONGLONG"
>dbi_result_get_longlong</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-LONGLONG-IDX"
>dbi_result_get_longlong_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-LONGLONG"
>dbi_result_bind_longlong</A
></TD
></TR
><TR
><TD
>unsigned long long</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-ULONGLONG"
>dbi_result_get_ulonglong</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-ULONGLONG-IDX"
>dbi_result_get_ulonglong_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-ULONGLONG"
>dbi_result_bind_ulonglong</A
></TD
></TR
><TR
><TD
>float</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-FLOAT"
>dbi_result_get_float</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-FLOAT-IDX"
>dbi_result_get_float_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-FLOAT"
>dbi_result_bind_float</A
></TD
></TR
><TR
><TD
>double</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-DOUBLE"
>dbi_result_get_double</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-DOUBLE-IDX"
>dbi_result_get_double_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-DOUBLE"
>dbi_result_bind_double</A
></TD
></TR
><TR
><TD
>character string</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-STRING"
>dbi_result_get_string</A
>, <A
HREF="reference-field.html#DBI-RESULT-GET-STRING-COPY"
>dbi_result_get_string_copy</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-STRING-IDX"
>dbi_result_get_string_idx</A
>, <A
HREF="reference-field-idx.html#DBI-RESULT-GET-STRING-COPY-IDX"
>dbi_result_get_string_copy_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-STRING"
>dbi_result_bind_string</A
></TD
></TR
><TR
><TD
>binary string</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-BINARY"
>dbi_result_get_binary</A
>, <A
HREF="reference-field.html#DBI-RESULT-GET-BINARY-COPY"
>dbi_result_get_binary_copy</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-BINARY-IDX"
>dbi_result_get_binary_idx</A
>, <A
HREF="reference-field-idx.html#DBI-RESULT-GET-BINARY-COPY-IDX"
>dbi_result_get_binary_copy_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-BINARY"
>dbi_result_bind_binary</A
></TD
></TR
><TR
><TD
>date/time</TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-GET-DATETIME"
>dbi_result_get_datetime</A
></TD
><TD
><A
HREF="reference-field-idx.html#DBI-RESULT-GET-DATETIME-IDX"
>dbi_result_get_datetime_idx</A
></TD
><TD
><A
HREF="reference-field.html#DBI-RESULT-BIND-DATETIME"
>dbi_result_bind_datetime</A
></TD
></TR
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