pg_prepare
(PHP 5 >= 5.1.0, PHP 7, PHP 8)
pg_prepare — Submits a request to create a prepared statement with the given parameters, and waits for completion
说明
pg_prepare() creates a prepared statement for later execution with pg_execute() or pg_send_execute(). This feature allows commands that will be used repeatedly to be parsed and planned just once, rather than each time they are executed. pg_prepare() is supported only against PostgreSQL 7.4 or higher connections; it will fail when using earlier versions.
The function creates a prepared statement named stmtname from the query
string, which must contain a single SQL command. stmtname may be "" to
create an unnamed statement, in which case any pre-existing unnamed
statement is automatically replaced; otherwise it is an error if the
statement name is already defined in the current session. If any parameters
are used, they are referred to in the query as $1, $2, etc.
Prepared statements for use with pg_prepare() can also be created by
executing SQL PREPARE statements. (But pg_prepare() is more flexible since it
does not require parameter types to be pre-specified.) Also, although there
is no PHP function for deleting a prepared statement, the SQL DEALLOCATE
statement can be used for that purpose.
参数
-
connection -
An PgSql\Connection instance. When
connectionis unspecified, the default connection is used. The default connection is the last connection made by pg_connect() or pg_pconnect(). -
stmtname -
The name to give the prepared statement. Must be unique per-connection. If "" is specified, then an unnamed statement is created, overwriting any previously defined unnamed statement.
-
query -
The parameterized SQL statement. Must contain only a single statement. (multiple statements separated by semi-colons are not allowed.) If any parameters are used, they are referred to as $1, $2, etc.
返回值
An PgSql\Result instance on success, 或者在失败时返回 false.
更新日志
| 版本 | 说明 |
|---|---|
| 8.1.0 | 现在返回 PgSql\Result 实例，之前返回 资源(resource) |
| 8.1.0 |
现在 connection 参数接受 PgSql\Connection
实例，之前接受 资源(resource)。
|
范例
示例 #1 Using pg_prepare()
<?php
// Connect to a database named "mary"
$dbconn = pg_connect("dbname=mary");
// Prepare a query for execution
$result = pg_prepare($dbconn, "my_query", 'SELECT * FROM shops WHERE name = $1');
// Execute the prepared query. Note that it is not necessary to escape
// the string "Joe's Widgets" in any way
$result = pg_execute($dbconn, "my_query", array("Joe's Widgets"));
// Execute the same prepared query, this time with a different parameter
$result = pg_execute($dbconn, "my_query", array("Clothes Clothes Clothes"));
?>
参见
- pg_execute() - Sends a request to execute a prepared statement with given parameters, and waits for the result
- pg_send_execute() - Sends a request to execute a prepared statement with given parameters, without waiting for the result(s)
add a note
User Contributed Notes 6 notes
SQL is often a complicated piece of code by itself, so you may wish put it inside a "here doc." This will help you read it wherever it appears and test it by itself via a command-line or gui client.
$sql = <<<SQL
SELECT a.foo, b.bar, c.baz
FROM
table_a a
LEFT JOIN
table_b b
ON (
a.a_id = b.a_id
)
JOIN
table_c c
ON (
b.c_id = c.c_id
)
WHERE c.name = $1
SQL;
I had some problems with this function. When you use pg_prepare() with a function like date_trunc('day', $1) you need to specify the data type.
The solution was use the Pear MDB2 but with some changes in code. The original code try to use pg_prepare() too, with errors.
The given name cannot be the statement itself.
It has a maximum length and will truncate.
If two queries begin the same way, only the first one will be used.
If you decide to deallocate (unprepare) a previously prepared sql command it might be better to quote the sql name as in
DEALLOCATE "theNameOfMySQL"
instead of (the more natural)
DEALLOCATE theNameOfMySQL
PostgerSQL preserves the case of your identifiers if, and only if, you quote them. The pg_prepare function preserves the case of the sql name you use.
A complete example would be
$sql = 'SELECT * FROM user WHERE cod_user = $1';
$sqlName = 'selectUserByCode';
if (!pg_prepare ($sqlName, $sql)) {
die("Can't prepare '$sql': " . pg_last_error());
}
$rs = pg_execute($sqlName, array(1));
do whatever you want with $rs and finally
$sql = sprintf(
'DEALLOCATE "%s"',
pg_escape_string($sqlName)
);
if(!pg_query($sql)) {
die("Can't query '$sql': " . pg_last_error());
}
Note that if you are preparing a query with an in clause with a list of items, you will need to prepare each item separately.
$result = pg_prepare($dbconn, "my_query", 'SELECT * FROM shops WHERE name IN($1,$2,$3)');
$result = pg_execute($dbconn, "my_query", array("coffee", "beer", "hard"));
This means that you can't just prepare a query with an arbitrary in() list.