丢失了对 INFORMATION_SCHEMA.COLUMNS Table 和 table 连接的查询

Question

我正在尝试将 DISTINCT B.INDEX_NAME 与 B.COLUMN_NAME 一起带回来。这就是我使用

分组的原因

然后对于返回的每一行我需要 A.DATA_TYPE

A.DATA_TYPE返回不正确

SELECT  A.DATA_TYPE, B.INDEX_NAME,  B.COLUMN_NAME
FROM  INFORMATION_SCHEMA.COLUMNS as A, INFORMATION_SCHEMA.STATISTICS as B
where B.TABLE_SCHEMA= "mySchema"
and   B.TABLE_NAME  = "myTable"
and   A.TABLE_SCHEMA = B.TABLE_SCHEMA
and   A.TABLE_NAME   = B.TABLE_NAME
GROUP BY B.COLUMN_NAME

Answer 1

您的问题是由 GROUP BY 子句从返回的多个值中随机选择 DATA_TYPE 引起的，因为您的 JOIN 没有条件。您需要做的是通过向 JOIN:

添加条件，将每个列名的值数限制为 1

SELECT A.DATA_TYPE, B.INDEX_NAME, B.COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS AS A
JOIN INFORMATION_SCHEMA.STATISTICS AS B
ON A.TABLE_SCHEMA = B.TABLE_SCHEMA AND
   A.TABLE_NAME = B.TABLE_NAME AND
   A.COLUMN_NAME = B.COLUMN_NAME
WHERE A.TABLE_SCHEMA= "mySchema" AND 
      A.TABLE_NAME  = "myTable"

在 PHP 中（使用 MySQLI）：

$sql = 'SELECT A.DATA_TYPE, B.INDEX_NAME, B.COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS AS A
JOIN INFORMATION_SCHEMA.STATISTICS AS B
ON A.TABLE_SCHEMA = B.TABLE_SCHEMA AND
   A.TABLE_NAME = B.TABLE_NAME AND
   A.COLUMN_NAME = B.COLUMN_NAME
WHERE A.TABLE_SCHEMA= "mySchema" AND 
      A.TABLE_NAME  = "myTable"';
$result = mysqli_query($conn, $sql);
echo mysqli_num_rows($result);
while ($row = mysqli_fetch_assoc($result)) print_r($row);

丢失了对 INFORMATION_SCHEMA.COLUMNS Table 和 table 连接的查询

lost doing a query against INFORMATION_SCHEMA.COLUMNS Table with a table join

mysql

metadata