使用SHOW INDEX，如下所示：

SHOW INDEX FROM [tablename]

文档：https://dev.mysql.com/doc/refman/5.0/en/show-index.html

尝试：

SELECT * FROM information_schema.statistics 
  WHERE table_schema = [DATABASE NAME] 
    AND table_name = [TABLE NAME] AND column_name = [COLUMN NAME]

它会告诉你某一列上是否有任何类型的索引，而不需要知道索引的名称。它也将在存储过程中工作（与显示索引相反）

show index from table_name where Column_name= column_name ;

SHOW KEYS FROM  tablename WHERE Key_name= unique key name 

将显示表中是否存在唯一键。

使用以下语句：

SHOW INDEX FROM *your_table*

然后检查字段的结果：row[“Table”]，row[“Key_name”]

确保正确写入“Key_name”

要从CLI查看表的布局，您可以使用

desc mytable

或

show table mytable

补充GK10的建议：

使用以下语句：SHOW INDEX FROM your_table

And then check the result for the fields: row["Table"], row["Key_name"]

确保正确写入“Key_name”

可以将其应用到PHP（或其他语言）中，并将其封装在sql语句中，以查找索引列。基本上，您可以将SHOW INDEX FROM mytable的结果拉入PHP，然后使用column_name列来获取索引列。

制作数据库连接字符串并执行以下操作：

$mysqli = mysqli_connect("localhost", "my_user", "my_password", "world");

$sql =  "SHOW INDEX FROM  mydatabase.mytable  WHERE Key_name =  PRIMARY ;" ;
$result = mysqli_query($mysqli, $sql);

while ($row = $result->fetch_assoc()) {
    echo $rowVerbatimsSet["Column_name"];
}

尝试使用此选项：

SELECT TRUE
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
WHERE TABLE_SCHEMA = "{DB_NAME}" 
AND TABLE_NAME = "{DB_TABLE}"
AND COLUMN_NAME = "{DB_INDEXED_FIELD}";

您可以使用以下SQL来检查表上给定的列是否已编入索引：

select  a.table_schema, a.table_name, a.column_name, index_name
from    information_schema.columns a
join    information_schema.tables  b on a.table_schema  = b.table_schema and
                                    a.table_name = b.table_name and 
                                    b.table_type =  BASE TABLE 
left join (
 select     concat(x.name,  / , y.name) full_path_schema, y.name index_name
 FROM   information_schema.INNODB_SYS_TABLES  as x
 JOIN   information_schema.INNODB_SYS_INDEXES as y on x.TABLE_ID = y.TABLE_ID
 WHERE  x.name =  your_schema 
 and    y.name =  your_column ) d on concat(a.table_schema,  / , a.table_name,  / , a.column_name) = d.full_path_schema
where   a.table_schema =  your_schema 
and     a.column_name  =  your_column 
order by a.table_schema, a.table_name;

由于联接是针对INNODB_SYS_*的，因此匹配索引仅来自INNODB表。

If you need to check if a index for a column exists as a database function, you can use/adopt this code. If you want to check if an index exists at all regardless of the position in a multi-column-index, then just delete the part AND SEQ_IN_INDEX = 1.

DELIMITER $$
CREATE FUNCTION `fct_check_if_index_for_column_exists_at_first_place`(
    `IN_SCHEMA` VARCHAR(255),
    `IN_TABLE` VARCHAR(255),
    `IN_COLUMN` VARCHAR(255)
)
RETURNS tinyint(4)
LANGUAGE SQL
DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT  Check if index exists at first place in sequence for a given column in a given table in a given schema. Returns -1 if schema does not exist. Returns -2 if table does not exist. Returns -3 if column does not exist. If index exists in first place it returns 1, otherwise 0. 
BEGIN

-- Check if index exists at first place in sequence for a given column in a given table in a given schema. 
-- Returns -1 if schema does not exist. 
-- Returns -2 if table does not exist. 
-- Returns -3 if column does not exist. 
-- If the index exists in first place it returns 1, otherwise 0.
-- Example call: SELECT fct_check_if_index_for_column_exists_at_first_place( schema_name ,  table_name ,  index_name );

-- check if schema exists
SELECT 
    COUNT(*) INTO @COUNT_EXISTS
FROM 
    INFORMATION_SCHEMA.SCHEMATA
WHERE 
    SCHEMA_NAME = IN_SCHEMA
;

IF @COUNT_EXISTS = 0 THEN
    RETURN -1;
END IF;


-- check if table exists
SELECT 
    COUNT(*) INTO @COUNT_EXISTS
FROM 
    INFORMATION_SCHEMA.TABLES
WHERE 
    TABLE_SCHEMA = IN_SCHEMA
AND TABLE_NAME = IN_TABLE
;

IF @COUNT_EXISTS = 0 THEN
    RETURN -2;
END IF;


-- check if column exists
SELECT 
    COUNT(*) INTO @COUNT_EXISTS
FROM 
    INFORMATION_SCHEMA.COLUMNS
WHERE 
    TABLE_SCHEMA = IN_SCHEMA
AND TABLE_NAME = IN_TABLE
AND COLUMN_NAME = IN_COLUMN
;

IF @COUNT_EXISTS = 0 THEN
    RETURN -3;
END IF;

-- check if index exists at first place in sequence
SELECT 
    COUNT(*) INTO @COUNT_EXISTS
FROM 
    information_schema.statistics 
WHERE 
    TABLE_SCHEMA = IN_SCHEMA
AND TABLE_NAME = IN_TABLE AND COLUMN_NAME = IN_COLUMN
AND SEQ_IN_INDEX = 1;


IF @COUNT_EXISTS > 0 THEN
    RETURN 1;
ELSE
    RETURN 0;
END IF;


END$$
DELIMITER ;