有没有办法从 mysql 数据库中获取主键字段的名称?例如:
我有一张这样的桌子:
id | 姓名 |
---|---|
1 | Foo1 |
2 | Foo2 |
3 | Foo3 |
字段 id 是主键的地方(它有自动递增,但我不能使用它)。如何在 php 中检索字段名称“id”?
更好的方法是使用
SHOW KEYS
,因为您并不总是可以访问 information_schema。以下作品:
SHOW KEYS FROM table WHERE Key_name = 'PRIMARY'
Column_name 将包含主键的名称。
这里是主键列名
SELECT k.column_name
FROM information_schema.table_constraints t
JOIN information_schema.key_column_usage k
USING(constraint_name,table_schema,table_name)
WHERE t.constraint_type='PRIMARY KEY'
AND t.table_schema='YourDatabase'
AND t.table_name='YourTable';
SELECT kcu.column_name, kcu.ordinal_position
FROM information_schema.table_constraints tc
INNER JOIN information_schema.key_column_usage kcu
ON tc.CONSTRAINT_CATALOG = kcu.CONSTRAINT_CATALOG
AND tc.CONSTRAINT_SCHEMA = kcu.CONSTRAINT_SCHEMA
AND tc.CONSTRAINT_NAME = kcu.CONSTRAINT_NAME
WHERE tc.table_schema = schema() -- only look in the current schema
AND tc.constraint_type = 'PRIMARY KEY'
AND tc.table_name = '<your-table-name>' -- specify your table.
ORDER BY kcu.ordinal_position
使用:
show columns from tablename where `Key` = "PRI";
这个怎么样:
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'Your Database'
AND TABLE_NAME = 'Your Table name'
AND COLUMN_KEY = 'PRI';
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'Your Database'
AND TABLE_NAME = 'Your Table name'
AND COLUMN_KEY = 'UNI';
如果您想通过 PHP 一次性动态生成主键列表,而不必遍历每个表,您可以使用
SELECT TABLE_NAME, COLUMN_NAME
FROM INFORMATION_SCHEMA.key_column_usage
WHERE table_schema = '$database_name' AND CONSTRAINT_NAME = 'PRIMARY'
尽管您确实需要访问 information.schema 才能执行此操作。
最短的代码似乎是
// $dblink contain database login details
// $tblName the current table name
$r = mysqli_fetch_assoc(mysqli_query($dblink, "SHOW KEYS FROM $tblName WHERE Key_name = 'PRIMARY'"));
$iColName = $r['Column_name'];
对于 PHP 方法,您可以使用 mysql_field_flags
$q = mysql_query('select * from table limit 1');
for($i = 0; $i < mysql_num_fields(); $i++)
if(strpos(mysql_field_tags($q, $i), 'primary_key') !== false)
echo mysql_field_name($q, $i)." is a primary key\n";
我终于明白了!
<?php
function mysql_get_prim_key($table){
$sql = "SHOW INDEX FROM $table WHERE Key_name = 'PRIMARY'";
$gp = mysql_query($sql);
$cgp = mysql_num_rows($gp);
if ($cgp > 0) {
// Note I'm not using a while loop because I never use more than one prim key column
$agp = mysql_fetch_array($gp);
extract($agp);
return($Column_name);
} else {
return(false);
}
}
?>
我使用 SHOW INDEX FROM table ;它给了我很多信息;如果键是唯一的,它在索引中的序列,排序规则,子部分,如果为空,它的类型和评论如果存在,请看这里的截图
MySQL 有一个 SQL 查询“SHOW INDEX FROM”,它返回表中的索引。 例如。 - 以下查询将显示产品表的所有索引:-
SHOW INDEXES FROM products \G
它返回一个包含类型、column_name、Key_name 等的表,并将所有索引和主键的输出显示为 -
*************************** 1. row ***************************
Table: products
Non_unique: 0
Key_name: PRIMARY
Seq_in_index: 1
Column_name: product_id
Collation: A
Cardinality: 0
Sub_part: NULL
Packed: NULL
Null:
Index_type: BTREE
Comment:
Index_comment:
要仅显示表中的主键,请使用:-
SHOW INDEXES FROM table_name WHERE Key_name = 'PRIMARY'
如果您的数据库中有空间表,请使用:
SHOW KEYS FROM table WHERE Key_name = 'PRIMARY' OR Key_name = 'OGR_FID'
你应该使用 PRIMARY 来自
key_column_usage.constraint_name = "PRIMARY"
示例查询,
SELECT k.column_name as PK, concat(tbl.TABLE_SCHEMA, '.`', tbl.TABLE_NAME, '`') as TABLE_NAME
FROM information_schema.TABLES tbl
JOIN information_schema.key_column_usage k on k.table_name = tbl.table_name
WHERE k.constraint_name='PRIMARY'
AND tbl.table_schema='MYDB'
AND tbl.table_type="BASE TABLE";
SELECT k.column_name
FROM information_schema.key_column_usage k
WHERE k.table_name = 'YOUR TABLE NAME' AND k.constraint_name LIKE 'pk%'
我建议您观看所有领域