php 使用 select 语句从数据库表中检索数据。具体语法为:select column1, column2, ... from table_name [where condition1 and condition2 and ...] [group by column_name] [order by column_name] [limit row_count] [offset row_offset]。示例:检索所有用户数据为 $sql = "select * from users&
PHP 中如何使用 SELECT 查询
SELECT 语句用于从数据库表中检索数据。以下是在 PHP 中使用 SELECT 查询的示例:
$sql = "SELECT * FROM users";
$query = $db->prepare($sql);
$query->execute();
while ($row = $query->fetch()) {
echo $row['name'] . " " . $row['email'] . "n";
}
语法
SELECT column1, column2, ...
FROM table_name
WHERE condition1 AND condition2 AND ...
GROUP BY column_name
ORDER BY column_name
LIMIT row_count
OFFSET row_offset
参数说明
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- SELECT: 指定要检索的列。
- FROM: 指定要检索数据的表。
- WHERE: 指定过滤数据的条件。
- GROUP BY: 对结果进行分组。
- ORDER BY: 对结果进行排序。
- LIMIT: 限制结果的行数。
- OFFSET: 从结果中跳过指定数量的行。
示例
检索所有用户数据:
$sql = "SELECT * FROM users";
检索特定列的数据:
$sql = "SELECT name, email FROM users";
过滤数据:
$sql = "SELECT * FROM users WHERE age > 18";
分组数据:
$sql = "SELECT city, COUNT(*) AS num_users FROM users GROUP BY city";
排序数据:
$sql = "SELECT * FROM users ORDER BY name";
限制结果:
$sql = "SELECT * FROM users LIMIT 10";
跳过结果:
$sql = "SELECT * FROM users OFFSET 10";