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Documentation updates in preparation for the release of version 3.0.0. (CVS 1613)
FossilOrigin-Name: 9fb29f7331254b601b71f0fe7d77f91915272dc7
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drh
161
www/capi3.tcl
161
www/capi3.tcl
@@ -1,4 +1,4 @@
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set rcsid {$Id: capi3.tcl,v 1.3 2004/06/01 10:01:25 drh Exp $}
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set rcsid {$Id: capi3.tcl,v 1.4 2004/06/17 19:04:17 drh Exp $}
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source common.tcl
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header {C/C++ Interface For SQLite Version 3}
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puts {
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@@ -27,6 +27,7 @@ requires incompatible changes to the database file format. Other
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incompatible changes, such as a cleanup of the API, were introduced
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at the same time under the theory that it is best to get your
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incompatible changes out of the way all at once.
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</p>
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<p>
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The API for version 3.0 is similar to the version 2.X API,
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@@ -48,12 +49,37 @@ to whatever datatype is appropriate for their system.
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<h3>2.0 C/C++ Interface</h3>
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<p>
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The API for SQLite 3.0 three includes 83 separate functions in addition
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to several data structures and #defines. (A complete
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<a href="capi3ref.html">API reference</a> is provided as a separate document.)
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Fortunately, the interface is not nearly as complex as its size implies.
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Simple programs can still make due with only 3 functions:
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<a href="capi3ref.html#sqlite3_open">sqlite3_open()</a>,
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<a href="capi3ref.html#sqlite3_exec">sqlite3_exec()</a>, and
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<a href="capi3ref.html#sqlite3_close">sqlite3_close()</a>.
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More control over the execution of the database engine is provided
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using
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<a href="capi3ref.html#sqlite3_prepare">sqlite3_prepare()</a>
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to compile an SQLite statement into byte code and
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<a href="capi3ref.html#sqlite3_prepare">sqlite3_step()</a>
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to execute that bytecode.
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A family of routines with names beginning with
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<a href="capi3ref.html#sqlite3_column_blob">sqlite3_column_</a>
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is used to extract informatiom about the result set of a query.
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Many interface functions come in pairs, with both a UTF-8 and
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and UTF-16 version. And there is a collection of routines
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used to implement user-defined SQL functions and user-defined
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text collating sequences.
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</p>
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<h4>2.1 Opening and closing a database</h4>
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<blockquote><pre>
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typedef struct sqlite3 sqlite3;
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int sqlite3_open(const char*, sqlite3**, const char**);
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int sqlite3_open16(const void*, sqlite3**, const char**);
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int sqlite3_open(const char*, sqlite3**);
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int sqlite3_open16(const void*, sqlite3**);
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int sqlite3_close(sqlite3*);
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const char *sqlite3_errmsg(sqlite3*);
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const void *sqlite3_errmsg16(sqlite3*);
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@@ -62,7 +88,8 @@ to whatever datatype is appropriate for their system.
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<p>
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The sqlite3_open() routine returns an integer error code rather than
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a pointer to the sqlite3 structure. The difference between sqlite3_open()
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a pointer to the sqlite3 structure as the version 2 interface did.
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The difference between sqlite3_open()
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and sqlite3_open16() is that sqlite3_open16() takes UTF-16 (in host native
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byte order) for the name of the database file. If a new database file
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needs to be created, then sqlite3_open16() will set the internal text
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@@ -71,12 +98,10 @@ representation to UTF-8.
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</p>
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<p>
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The third "const char**" argument to sqlite3_open() is a NULL-terminated
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list of keyword/value pairs that define options to apply to the open
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request. The third argument may be NULL if there are no options.
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This extra argument provides an expandable way of supporting new features
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in future releases. For example, a future release may contain an
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option to define an encryption/decryption key.
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The opening and/or creating of the database file is deferred until the
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file is actually needed. This allows options and parameters, such
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as the native text representation and default page size, to be
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set using PRAGMA statements.
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</p>
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<p>
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@@ -125,25 +150,57 @@ They are as follows:
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<h4>2.2 Executing SQL statements</h4>
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<blockquote><pre>
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typedef int (*sqlite_callback)(void*,int,char**, char**);
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int sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void*, char**);
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</pre></blockquote>
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<p>
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The sqlite3_exec function works much as it did in SQLite version 2.
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Zero or more SQL statements specified in the second parameter are compiled
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and executed. Query results are returned to a callback routine.
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See the <a href="capi3ref.html#sqlite3_exec">API reference</a> for additional
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information.
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</p>
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<p>
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In SQLite version 3, the sqlite3_exec routine is just a wrapper around
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calls to the prepared statement interface.
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</p>
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<blockquote><pre>
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typedef struct sqlite3_stmt sqlite3_stmt;
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int sqlite3_prepare(sqlite3*, const char*, sqlite3_stmt**, const char**);
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int sqlite3_prepare16(sqlite3*, const void*, sqlite3_stmt**, const void**);
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int sqlite3_prepare(sqlite3*, const char*, int, sqlite3_stmt**, const char**);
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int sqlite3_prepare16(sqlite3*, const void*, int, sqlite3_stmt**, const void**);
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int sqlite3_finalize(sqlite3_stmt*);
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int sqlite3_reset(sqlite3_stmt*);
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</pre></blockquote>
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<p>
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The non-callback API is now the preferred way of accessing the database.
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Wrapper functions that emulate the older callback API may (or may not)
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be provided.
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The sqlite3_prepare interface compiles a single SQL statement into byte code
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for later execution.
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This interface is now the preferred way of accessing the database.
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</p>
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<p>
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The sqlite3_prepare() function compiles an single SQL statement.
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The statement may contain tokens of the form "?" or "?nnn" or ":nnn:"
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The SQL statement is a UTF-8 string for sqlite3_prepare().
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The sqlite3_prepare16() works the same way except
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that it expects a UTF-16 string as SQL input.
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Only the first SQL statement in the input string is compiled.
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The fourth parameter is filled in with a pointer to the next (uncompiled)
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SQLite statement in the input string, if any.
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The sqlite3_finalize() routine deallocates a prepared SQL statement.
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All prepared statements must be finalized before the database can be
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closed.
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The sqlite3_reset() routine resets a prepared SQL statement so that it
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can be executed again.
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</p>
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<p>
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The SQL statement may contain tokens of the form "?" or "?nnn" or ":nnn:"
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where "nnn" is an integer. Such tokens represent unspecified literal values
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(or wildcard) to be filled in later by the sqlite3_bind() API.
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(or wildcards) to be filled in later by the
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<a href="capi3ref.html#sqlite3_bind_blob">sqlite3_bind</a> interface.
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Each wildcard as an associated number given
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by the "nnn" that follows the "?". If the "?" is not followed by an
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integer, then its number one more than the number of prior wildcards
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@@ -153,26 +210,14 @@ all instance of that wildcard will be filled in with the same value.
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Unbound wildcards have a value of NULL.
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</p>
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<p>The SQL statement is a UTF-8 string for sqlite3_prepare().
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The sqlite3_prepare16() works the same way except
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that it expects a UTF-16 string as SQL input.
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Only the first SQL statement in the input string is compiled.
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The fourth parameter is filled in with a pointer to the next (uncompiled)
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SQLite statement in the input string, if any.
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The sqlite3_finalize() routine deallocates a prepared SQL statement.
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The sqlite3_reset() routine resets a prepared SQL statement so that it
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can be executed again.
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</p>
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<blockquote><pre>
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int sqlite3_bind_blob(sqlite3_stmt*, int, const void*, int n, int eCopy);
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int sqlite3_bind_blob(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
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int sqlite3_bind_double(sqlite3_stmt*, int, double);
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int sqlite3_bind_int(sqlite3_stmt*, int, int);
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int sqlite3_bind_int64(sqlite3_stmt*, int, long long int);
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int sqlite3_bind_null(sqlite3_stmt*, int);
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int sqlite3_bind_text(sqlite3_stmt*, int, const char*, int n, int eCopy);
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int sqlite3_bind_text16(sqlite3_stmt*, int, const void*, int n, int eCopy);
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int sqlite3_bind_text(sqlite3_stmt*, int, const char*, int n, void(*)(void*));
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int sqlite3_bind_text16(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
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int sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
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</pre></blockquote>
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@@ -202,26 +247,38 @@ of the result set:
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</p>
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<blockquote><pre>
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int sqlite3_column_count(sqlite3_stmt*);
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int sqlite3_column_type(sqlite3_stmt*,int);
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const char *sqlite3_column_decltype(sqlite3_stmt *, int i);
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const char *sqlite3_column_decltype16(sqlite3_stmt *, int i);
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const char *sqlite3_column_name(sqlite3_stmt*,int);
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const void *sqlite3_column_name16(sqlite3_stmt*,int);
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const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
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int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
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int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
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int sqlite3_column_count(sqlite3_stmt*);
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const char *sqlite3_column_decltype(sqlite3_stmt *, int iCol);
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const void *sqlite3_column_decltype16(sqlite3_stmt *, int iCol);
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double sqlite3_column_double(sqlite3_stmt*, int iCol);
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int sqlite3_column_int(sqlite3_stmt*, int iCol);
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long long int sqlite3_column_int64(sqlite3_stmt*, int iCol);
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const char *sqlite3_column_name(sqlite3_stmt*, int iCol);
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const void *sqlite3_column_name16(sqlite3_stmt*, int iCol);
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const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
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const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
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int sqlite3_column_type(sqlite3_stmt*, int iCol);
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</pre></blockquote>
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<p>
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The sqlite3_column_count() function returns the number of columns in
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the results set. The sqlite3_column_type() function returns the
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The
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<a href="capi3ref.html#sqlite3_column_count">sqlite3_column_count()</a>
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function returns the number of columns in
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the results set. sqlite3_column_count() can be called at any time after
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sqlite3_prepare().
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<a href="capi3ref.html#sqlite3_data_count">sqlite3_data_count()</a>
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works similarly to
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sqlite3_column_count() except that it only works following sqlite3_step().
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If the previous call to sqlite3_step() returned SQLITE_DONE or an error code,
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then sqlite3_data_count() will return 0 whereas sqlite3_column_count() will
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continue to return the number of columns in the result set.
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</p>
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<p>
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The sqlite3_column_type() function returns the
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datatype for the value in the Nth column. The return value is one
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of these:
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</p>
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@@ -252,6 +309,12 @@ sqlite3_column_int64() returns 64-bit INTEGER data.
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Finally, sqlite3_column_double() return floating point data.
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</p>
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<p>
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It is not necessary to retrieve data in the format specify by
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sqlite3_column_type(). If a different format is requested, the data
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is converted automatically.
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</p>
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<h4>2.3 User-defined functions</h4>
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<p>
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@@ -265,7 +328,6 @@ User defined functions can be created using the following routine:
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const char *zFunctionName,
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int nArg,
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int eTextRep,
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int iCollateArg,
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void*,
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void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
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void (*xStep)(sqlite3_context*,int,sqlite3_value**),
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@@ -276,16 +338,16 @@ User defined functions can be created using the following routine:
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const void *zFunctionName,
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int nArg,
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int eTextRep,
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int iCollateArg,
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void*,
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void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
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void (*xStep)(sqlite3_context*,int,sqlite3_value**),
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void (*xFinal)(sqlite3_context*)
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);
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#define SQLITE3_UTF8 1
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#define SQLITE3_UTF16LE 2
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#define SQLITE3_UTF16 2
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#define SQLITE3_UTF16BE 3
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#define SQLITE3_ANY 4
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#define SQLITE3_UTF16LE 4
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#define SQLITE3_ANY 5
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</pre></blockquote>
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<p>
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@@ -297,9 +359,6 @@ be one of the parameters defined above. SQLite version 3 allows multiple
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implementations of the same function using different text representations.
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The database engine chooses the function that minimization the number
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of text conversions required.
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The iCollateArg parameter indicates that the collating sequence for the
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result is to be the same as the collating sequence of the iCollateArg-th
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parameter.
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</p>
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<p>
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@@ -341,15 +400,15 @@ to report results:
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<blockquote><pre>
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void *sqlite3_aggregate_context(sqlite3_context*, int nbyte);
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void *sqlite3_user_data(sqlite3_context*);
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void sqlite3_result_blob(sqlite3_context*, const void*, int n, int eCopy);
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void sqlite3_result_blob(sqlite3_context*, const void*, int n, void(*)(void*));
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void sqlite3_result_double(sqlite3_context*, double);
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void sqlite3_result_error(sqlite3_context*, const char*, int);
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void sqlite3_result_error16(sqlite3_context*, const void*, int);
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void sqlite3_result_int(sqlite3_context*, int);
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void sqlite3_result_int64(sqlite3_context*, long long int);
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void sqlite3_result_null(sqlite3_context*);
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void sqlite3_result_text(sqlite3_context*, const char*, int n, int eCopy);
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void sqlite3_result_text16(sqlite3_context*, const void*, int n, int eCopy);
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void sqlite3_result_text(sqlite3_context*, const char*, int n, void(*)(void*));
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void sqlite3_result_text16(sqlite3_context*, const void*, int n, void(*)(void*));
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void sqlite3_result_value(sqlite3_context*, sqlite3_value*);
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void *sqlite3_get_auxdata(sqlite3_context*, int);
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void sqlite3_set_auxdata(sqlite3_context*, int, void*, void (*)(void*));
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