Question

在Mysql之后UNION SELECT $ stmt。我从多个表中获取数据，现在任务是从实际表中选择id

我以前得到的数据是

$stmt = $DB_con->prepare('SELECT * FROM city UNION SELECT * FROM fruit ORDER BY CreatedTime ASC LIMIT 15');

$stmt->execute();

if($stmt->rowCount() > 0)
{
    while($row=$stmt->fetch(PDO::FETCH_ASSOC))
    {
        extract($row);

echo $ id; echo $ userName;

我得到了类似的数据 1 - hyderavbads 2 - 香蕉 3 - 橙色 4 - 德里

现在我需要选择实际的id并从原始表中获取值

Answer 1

使用当前查询无法从联合结果中了解原始表。

您可能希望将查询更改为此类内容，以便了解该ID的原始表格

SELECT id,value,'city' as tblName FROM city UNION SELECT id,value,'fruit' as tblName FROM fruit

Answer 2

尝试下面的代码，这是逻辑如何实现，检查并告诉我们是否有任何问题。

mysql> create table city(id int, city_name varchar(20));
Query OK, 0 rows affected (0.35 sec)

mysql> create table fruits(id int, fruit_name varchar(20));
Query OK, 0 rows affected (0.40 sec)

mysql> insert into city values(1,'Hyderabad');
Query OK, 1 row affected (0.04 sec)

mysql> insert into fruits values(1,'Banana');
Query OK, 1 row affected (0.06 sec)

mysql> SELECT id,city_name,'city' source FROM city UNION  SELECT id,fruit_name,'fruits' FROM fruits;
+------+-----------+--------+
| id   | city_name | source |
+------+-----------+--------+
|    1 | Hyderabad | city   |
|    1 | Banana    | fruits |
+------+-----------+--------+
2 rows in set (0.01 sec)


$stmt = $DB_con->prepare('SELECT id,city_name FROM city UNION SELECT id,fruit_name FROM fruit ORDER BY CreatedTime ASC LIMIT 15');

$stmt->execute();

if($stmt->rowCount() > 0)
{
    while($row=$stmt->fetch(PDO::FETCH_ASSOC))
    {
        extract($row);

    ---write here a case/if statement like
    If($source=="city")
    {
        --again prepare the statement and select the data from city table like
        $stmt_city = $DB_con->prepare('SELECT id,city_name,other_col_val FROM city where id = $id');
    }
    else
    {
        --again prepare the statement and select the data from fruits table like
        $stmt_city = $DB_con->prepare('SELECT id,fruit_name,other_col_val FROM fruits where id = $id');
    }
    }
}

在Mysql UNION SELECT $ stmt之后..我从多个表中获取数据

2 个答案: