Macros | Typedefs | Functions
PreparedStatement.h File Reference

Detailed Description

A PreparedStatement represent a single SQL statement pre-compiled into byte code for later execution.

The SQL statement may contain in parameters of the form "?". Such parameters represent unspecified literal values (or "wildcards") to be filled in later by the various setter methods defined in this interface. Each in parameter has an associated index number which is its sequence in the statement. The first in '?' parameter has index 1, the next has index 2 and so on. A PreparedStatement is created by calling Connection_prepareStatement().

Consider this statement:

 INSERT INTO employee(name, picture) VALUES(?, ?)

There are two in parameters in this statement, the parameter for setting the name has index 1 and the one for the picture has index 2. To set the values for the in parameters we use a setter method. Assuming name has a string value we use PreparedStatement_setString(). To set the value of the picture we submit a binary value using the method PreparedStatement_setBlob().

String and blob parameter values are set by reference and must not "disappear" before either PreparedStatement_execute() or PreparedStatement_executeQuery() is called.

Example:

To summarize, here is the code in context.

PreparedStatement_T p = Connection_prepareStatement(con, "INSERT INTO employee(name, picture) VALUES(?, ?)");
PreparedStatement_setString(p, 1, "Kamiya Kaoru");
PreparedStatement_setBlob(p, 2, jpeg, jpeg_size);
PreparedStatement_execute(p);

Reuse:

A PreparedStatement can be reused. That is, the method PreparedStatement_execute() can be called one or more times to execute the same statement. Clients can also set new in parameter values and re-execute the statement as shown in this example:

PreparedStatement_T p = Connection_prepareStatement(con, "INSERT INTO employee(name, picture) VALUES(?, ?)");
for (int i = 0; employees[i]; i++)
{
       PreparedStatement_setString(p, 1, employees[i].name);
       PreparedStatement_setBlob(p, 2, employees[i].picture, employees[i].picture_size);
       PreparedStatement_execute(p);
}

Result Sets:

Here is another example where we use a Prepared Statement to execute a query which returns a Result Set:

PreparedStatement_T p = Connection_prepareStatement(con, "SELECT id FROM employee WHERE name LIKE ?"); 
PreparedStatement_setString(p, 1, "%oru%");
ResultSet_T r = PreparedStatement_executeQuery(p);
while (ResultSet_next(r))
       printf("employee.id = %d\n", ResultSet_getInt(r, 1));

A ResultSet returned from PreparedStatement_executeQuery() "lives" until the Prepared Statement is executed again or until the Connection is returned to the Connection Pool.

Date and Time

PreparedStatement provides PreparedStatement_setTimestamp() for setting a Unix timestamp value. To set SQL Date, Time or DateTime values, simply use PreparedStatement_setString() with a time string format understood by your database. For instance to set a SQL Date value,

  PreparedStatement_setString(p, parameterIndex, "2019-12-28");

A PreparedStatement is reentrant, but not thread-safe and should only be used by one thread (at the time).

See also
Connection.h ResultSet.h SQLException.h

Macros

#define T   PreparedStatement_T
 

Typedefs

typedef struct PreparedStatement_S * T
 

Functions

void PreparedStatement_execute (T P)
 Executes the prepared SQL statement, which may be an INSERT, UPDATE, or DELETE statement or an SQL statement that returns nothing, such as an SQL DDL statement. More...
 
ResultSet_T PreparedStatement_executeQuery (T P)
 Executes the prepared SQL statement, which returns a single ResultSet object. More...
 
long long PreparedStatement_rowsChanged (T P)
 Returns the number of rows that was inserted, deleted or modified by the most recently completed SQL statement on the database connection. More...
 
Parameters
void PreparedStatement_setString (T P, int parameterIndex, const char *x)
 Sets the in parameter at index parameterIndex to the given string value. More...
 
void PreparedStatement_setInt (T P, int parameterIndex, int x)
 Sets the in parameter at index parameterIndex to the given int value. More...
 
void PreparedStatement_setLLong (T P, int parameterIndex, long long x)
 Sets the in parameter at index parameterIndex to the given long long value. More...
 
void PreparedStatement_setDouble (T P, int parameterIndex, double x)
 Sets the in parameter at index parameterIndex to the given double value. More...
 
void PreparedStatement_setBlob (T P, int parameterIndex, const void *x, int size)
 Sets the in parameter at index parameterIndex to the given blob value. More...
 
void PreparedStatement_setTimestamp (T P, int parameterIndex, time_t x)
 Sets the in parameter at index parameterIndex to the given Unix timestamp value. More...
 
Properties
int PreparedStatement_getParameterCount (T P)
 Returns the number of parameters in this prepared statement. More...
 

Macro Definition Documentation

◆ T

#define T   PreparedStatement_T

Typedef Documentation

◆ T

typedef struct PreparedStatement_S* T

Function Documentation

◆ PreparedStatement_setString()

void PreparedStatement_setString ( T  P,
int  parameterIndex,
const char *  x 
)

Sets the in parameter at index parameterIndex to the given string value.

Parameters
PA PreparedStatement object
parameterIndexThe first parameter is 1, the second is 2,..
xThe string value to set. Must be a NUL terminated string. NULL is allowed to indicate a SQL NULL value.
Exceptions
SQLExceptionIf a database access error occurs or if parameter index is out of range
See also
SQLException.h

◆ PreparedStatement_setInt()

void PreparedStatement_setInt ( T  P,
int  parameterIndex,
int  x 
)

Sets the in parameter at index parameterIndex to the given int value.

In general, on both 32 and 64 bits architecture, int is 4 bytes or 32 bits and long long is 8 bytes or 64 bits. A long type is usually equal to int on 32 bits architecture and equal to long long on 64 bits architecture. However, the width of integer types are architecture and compiler dependent. The above is usually true, but not necessarily.

Parameters
PA PreparedStatement object
parameterIndexThe first parameter is 1, the second is 2,..
xThe int value to set
Exceptions
SQLExceptionIf a database access error occurs or if parameter index is out of range
See also
SQLException.h

◆ PreparedStatement_setLLong()

void PreparedStatement_setLLong ( T  P,
int  parameterIndex,
long long  x 
)

Sets the in parameter at index parameterIndex to the given long long value.

In general, on both 32 and 64 bits architecture, int is 4 bytes or 32 bits and long long is 8 bytes or 64 bits. A long type is usually equal to int on 32 bits architecture and equal to long long on 64 bits architecture. However, the width of integer types are architecture and compiler dependent. The above is usually true, but not necessarily.

Parameters
PA PreparedStatement object
parameterIndexThe first parameter is 1, the second is 2,..
xThe long long value to set
Exceptions
SQLExceptionIf a database access error occurs or if parameter index is out of range
See also
SQLException.h

◆ PreparedStatement_setDouble()

void PreparedStatement_setDouble ( T  P,
int  parameterIndex,
double  x 
)

Sets the in parameter at index parameterIndex to the given double value.

Parameters
PA PreparedStatement object
parameterIndexThe first parameter is 1, the second is 2,..
xThe double value to set
Exceptions
SQLExceptionIf a database access error occurs or if parameter index is out of range
See also
SQLException.h

◆ PreparedStatement_setBlob()

void PreparedStatement_setBlob ( T  P,
int  parameterIndex,
const void *  x,
int  size 
)

Sets the in parameter at index parameterIndex to the given blob value.

Parameters
PA PreparedStatement object
parameterIndexThe first parameter is 1, the second is 2,..
xThe blob value to set
sizeThe number of bytes in the blob
Exceptions
SQLExceptionIf a database access error occurs or if parameter index is out of range
See also
SQLException.h

◆ PreparedStatement_setTimestamp()

void PreparedStatement_setTimestamp ( T  P,
int  parameterIndex,
time_t  x 
)

Sets the in parameter at index parameterIndex to the given Unix timestamp value.

The timestamp value given in x is expected to be in the GMT timezone. For instance, a value returned by time(3) which represents the system's notion of the current Greenwich time. SQLite does not have temporal SQL data types per se and using this method with SQLite will store the timestamp value as a numerical type, as-is. This is usually what you want; it is fast, compact and unambiguous.

Parameters
PA PreparedStatement object
parameterIndexThe first parameter is 1, the second is 2,..
xThe GMT timestamp value to set. E.g. a value returned by time(3)
Exceptions
SQLExceptionIf a database access error occurs or if parameter index is out of range
See also
SQLException.h ResultSet_getTimestamp

◆ PreparedStatement_execute()

void PreparedStatement_execute ( T  P)

Executes the prepared SQL statement, which may be an INSERT, UPDATE, or DELETE statement or an SQL statement that returns nothing, such as an SQL DDL statement.

Parameters
PA PreparedStatement object
Exceptions
SQLExceptionIf a database error occurs
See also
SQLException.h

◆ PreparedStatement_executeQuery()

ResultSet_T PreparedStatement_executeQuery ( T  P)

Executes the prepared SQL statement, which returns a single ResultSet object.

A ResultSet "lives" only until the next call to a PreparedStatement method or until the Connection is returned to the Connection Pool. This means that Result Sets cannot be saved between queries.

Parameters
PA PreparedStatement object
Returns
A ResultSet object that contains the data produced by the prepared statement.
Exceptions
SQLExceptionIf a database error occurs
See also
ResultSet.h
SQLException.h

◆ PreparedStatement_rowsChanged()

long long PreparedStatement_rowsChanged ( T  P)

Returns the number of rows that was inserted, deleted or modified by the most recently completed SQL statement on the database connection.

If used with a transaction, this method should be called before commit is executed, otherwise 0 is returned.

Parameters
PA PreparedStatement object
Returns
The number of rows changed by the last (DIM) SQL statement

◆ PreparedStatement_getParameterCount()

int PreparedStatement_getParameterCount ( T  P)

Returns the number of parameters in this prepared statement.

Parameters
PA PreparedStatement object
Returns
The number of parameters in this prepared statement

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