sqlite/man/sqlite3_prepare.3

.Dd December 19, 2018
.Dt SQLITE3_PREPARE 3
.Os
.Sh NAME
.Nm sqlite3_prepare ,
.Nm sqlite3_prepare_v2 ,
.Nm sqlite3_prepare_v3 ,
.Nm sqlite3_prepare16 ,
.Nm sqlite3_prepare16_v2 ,
.Nm sqlite3_prepare16_v3
.Nd Compiling An SQL Statement
.Sh SYNOPSIS
.Ft int
.Fo sqlite3_prepare
.Fa "sqlite3 *db"
.Fa "const char *zSql"
.Fa "int nByte"
.Fa "sqlite3_stmt **ppStmt"
.Fa "const char **pzTail     "
.Fc
.Ft int
.Fo sqlite3_prepare_v2
.Fa "sqlite3 *db"
.Fa "const char *zSql"
.Fa "int nByte"
.Fa "sqlite3_stmt **ppStmt"
.Fa "const char **pzTail     "
.Fc
.Ft int
.Fo sqlite3_prepare_v3
.Fa "sqlite3 *db"
.Fa "const char *zSql"
.Fa "int nByte"
.Fa "unsigned int prepFlags"
.Fa "sqlite3_stmt **ppStmt"
.Fa "const char **pzTail     "
.Fc
.Ft int
.Fo sqlite3_prepare16
.Fa "sqlite3 *db"
.Fa "const void *zSql"
.Fa "int nByte"
.Fa "sqlite3_stmt **ppStmt"
.Fa "const void **pzTail     "
.Fc
.Ft int
.Fo sqlite3_prepare16_v2
.Fa "sqlite3 *db"
.Fa "const void *zSql"
.Fa "int nByte"
.Fa "sqlite3_stmt **ppStmt"
.Fa "const void **pzTail     "
.Fc
.Ft int
.Fo sqlite3_prepare16_v3
.Fa "sqlite3 *db"
.Fa "const void *zSql"
.Fa "int nByte"
.Fa "unsigned int prepFlags"
.Fa "sqlite3_stmt **ppStmt"
.Fa "const void **pzTail     "
.Fc
.Sh DESCRIPTION
To execute an SQL statement, it must first be compiled into a byte-code
program using one of these routines.
Or, in other words, these routines are constructors for the prepared statement
object.
.Pp
The preferred routine to use is sqlite3_prepare_v2().
The sqlite3_prepare() interface is legacy and should
be avoided.
sqlite3_prepare_v3() has an extra "prepFlags" option
that is used for special purposes.
.Pp
The use of the UTF-8 interfaces is preferred, as SQLite currently does
all parsing using UTF-8.
The UTF-16 interfaces are provided as a convenience.
The UTF-16 interfaces work by converting the input text into UTF-8,
then invoking the corresponding UTF-8 interface.
.Pp
The first argument, "db", is a database connection
obtained from a prior successful call to sqlite3_open(),
sqlite3_open_v2() or sqlite3_open16().
The database connection must not have been closed.
.Pp
The second argument, "zSql", is the statement to be compiled, encoded
as either UTF-8 or UTF-16.
The sqlite3_prepare(), sqlite3_prepare_v2(), and sqlite3_prepare_v3()
interfaces use UTF-8, and sqlite3_prepare16(), sqlite3_prepare16_v2(),
and sqlite3_prepare16_v3() use UTF-16.
.Pp
If the nByte argument is negative, then zSql is read up to the first
zero terminator.
If nByte is positive, then it is the number of bytes read from zSql.
If nByte is zero, then no prepared statement is generated.
If the caller knows that the supplied string is nul-terminated, then
there is a small performance advantage to passing an nByte parameter
that is the number of bytes in the input string <i>including</i> the
nul-terminator.
.Pp
If pzTail is not NULL then *pzTail is made to point to the first byte
past the end of the first SQL statement in zSql.
These routines only compile the first statement in zSql, so *pzTail
is left pointing to what remains uncompiled.
.Pp
*ppStmt is left pointing to a compiled prepared statement
that can be executed using sqlite3_step().
If there is an error, *ppStmt is set to NULL.
If the input text contains no SQL (if the input is an empty string
or a comment) then *ppStmt is set to NULL.
The calling procedure is responsible for deleting the compiled SQL
statement using sqlite3_finalize() after it has finished
with it.
ppStmt may not be NULL.
.Pp
On success, the sqlite3_prepare() family of routines return SQLITE_OK;
otherwise an error code is returned.
.Pp
The sqlite3_prepare_v2(), sqlite3_prepare_v3(), sqlite3_prepare16_v2(),
and sqlite3_prepare16_v3() interfaces are recommended for all new programs.
The older interfaces (sqlite3_prepare() and sqlite3_prepare16()) are
retained for backwards compatibility, but their use is discouraged.
In the "vX" interfaces, the prepared statement that is returned (the
sqlite3_stmt object) contains a copy of the original SQL
text.
This causes the sqlite3_step() interface to behave differently
in three ways:
.Bl -enum
.It
If the database schema changes, instead of returning SQLITE_SCHEMA
as it always used to do, sqlite3_step() will automatically
recompile the SQL statement and try to run it again.
As many as SQLITE_MAX_SCHEMA_RETRY retries will
occur before sqlite3_step() gives up and returns an error.
.It
When an error occurs, sqlite3_step() will return one
of the detailed error codes or extended error codes.
The legacy behavior was that sqlite3_step() would only
return a generic SQLITE_ERROR result code and the application
would have to make a second call to sqlite3_reset()
in order to find the underlying cause of the problem.
With the "v2" prepare interfaces, the underlying reason for the error
is returned immediately.
.It
If the specific value bound to  host parameter in the
WHERE clause might influence the choice of query plan for a statement,
then the statement will be automatically recompiled, as if there had
been a schema change, on the first  sqlite3_step() call
following any change to the  bindings of that parameter.
The specific value of WHERE-clause parameter might influence
the choice of query plan if the parameter is the left-hand side of
a LIKE or GLOB operator or if the parameter is compared to
an indexed column and the SQLITE_ENABLE_STAT3 compile-time
option is enabled.
.El
.Pp
<p> sqlite3_prepare_v3() differs from sqlite3_prepare_v2() only in
having the extra prepFlags parameter, which is a bit array consisting
of zero or more of the SQLITE_PREPARE_* flags.
The sqlite3_prepare_v2() interface works exactly the same as sqlite3_prepare_v3()
with a zero prepFlags parameter.
.Sh SEE ALSO
.Xr sqlite3 3 ,
.Xr sqlite3_stmt 3 ,
.Xr sqlite3_bind_blob 3 ,
.Xr sqlite3_finalize 3 ,
.Xr sqlite3_open 3 ,
.Xr sqlite3_prepare 3 ,
.Xr sqlite3_reset 3 ,
.Xr sqlite3_step 3 ,
.Xr sqlite3_stmt 3 ,
.Xr SQLITE_OK 3 ,
.Xr SQLITE_PREPARE_PERSISTENT 3 ,
.Xr SQLITE_OK 3