MySQL query to get column names?

Question

I'd like to get all of a mysql table's col names into an array in php?

Is there a query for this?

Answer 1

You can use following query for MYSQL:

SHOW columns FROM your-table;

Below is the example code which shows How to implement above syntax in php to list the names of columns:

$sql = "SHOW COLUMNS FROM your-table";
$result = mysqli_query($conn,$sql);
while($row = mysqli_fetch_array($result)){
    echo $row['Field']."<br>";
}

For Details about output of SHOW COLUMNS FROM TABLE visit: MySQL Refrence.

Answer 2

when you want to check your all table structure with some filed then use this code. In this query i select column_name,column_type and table_name for more details . I use order by column_type so i can see it easily.

SELECT `COLUMN_NAME`,COLUMN_TYPE,TABLE_NAME 
FROM `INFORMATION_SCHEMA`.`COLUMNS` 
WHERE `TABLE_SCHEMA`='yourdatabasename' order by DATA_TYPE;

If you want to check only double type filed then you can do it easily

SELECT `COLUMN_NAME`,COLUMN_TYPE,TABLE_NAME,DATA_TYPE 
FROM `INFORMATION_SCHEMA`.`COLUMNS` 
WHERE `TABLE_SCHEMA`='yourdatabasename' AND DATA_TYPE like '%bigint%'  order by DATA_TYPE;

if you want to check which field allow null type etc then you can use this

SELECT `COLUMN_NAME`,COLUMN_TYPE,TABLE_NAME,IS_NULLABLE,DATA_TYPE 
FROM `INFORMATION_SCHEMA`.`COLUMNS` 
WHERE `TABLE_SCHEMA`='yourdatabasename' and DATA_TYPE like '%bigint%' and IS_NULLABLE ='NO' order by COLUMN_TYPE;

you want to check more then thik link also help you.

https://dev.mysql.com/doc/refman/5.7/en/columns-table.html

Answer 3

SHOW COLUMNS in mysql 5.1 (not 5.5) uses a temporary disk table.

• http://dev.mysql.com/doc/refman/5.1/en/internal-temporary-tables.html
• http://dev.mysql.com/doc/refman/5.1/en/show-columns.html

So it can be considered slow for some cases. At least, it can bump up your created_tmp_disk_tables value. Imagine one temporary disk table per connection or per each page request.

SHOW COLUMNS is not really so slow, possibly because it uses file system cache. Phpmyadmin says ~0.5ms consistently. This is nothing compared to 500ms-1000ms of serving a wordpress page. But still, there are times it matters. There is a disk system involvement, you never know what happens when server is busy, cache is full, hdd is stalled etc.

Retrieving column names through SELECT * FROM ... LIMIT 1 was around ~0.1ms, and it can use query cache as well.

So here is my little optimized code to get column names from a table, without using show columns if possible:

function db_columns_ar($table)
{
//returns Array('col1name'=>'col1name','col2name'=>'col2name',...)
if(!$table) return Array();
if(!is_string($table)) return Array();

global $db_columns_ar_cache;
if(!empty($db_columns_ar_cache[$table]))
    return $db_columns_ar_cache[$table];


//IMPORTANT show columns creates a temp disk table
$cols=Array();
$row=db_row_ar($q1="SELECT * FROM `$table` LIMIT 1");
if($row)
    {
    foreach($row as $name=>$val)
        $cols[$name]=$name;
    }
else
    {
    $coldata=db_rows($q2="SHOW COLUMNS FROM `$table`");
    if($coldata)
        foreach($coldata as $row)
            $cols[$row->Field]=$row->Field;
    }
$db_columns_ar_cache[$table]=$cols;
//debugexit($q1,$q2,$row,$coldata,$cols);
return $cols;
}

Notes:

• As long as your tables first row does not contain megabyte range of data, it should work fine.
• The function names db_rows and db_row_ar should be replaced with your specific database setup.

Answer 4

An old PHP function "mysql_list_fields()" is deprecated. So, today the best way to get names of fields is a query "SHOW COLUMNS FROM table_name [LIKE 'name']". So, here is a little example:

$fields = array();
$res=mysql_query("SHOW COLUMNS FROM mytable");
while ($x = mysql_fetch_assoc($res)){
  $fields[] = $x['Field'];
}
foreach ($fields as $f) { echo "<br>Field name: ".$f; }

Answer 5

The best way is to use the INFORMATION_SCHEMA metadata virtual database. Specifically the INFORMATION_SCHEMA.COLUMNS table...

SELECT `COLUMN_NAME` 
FROM `INFORMATION_SCHEMA`.`COLUMNS` 
WHERE `TABLE_SCHEMA`='yourdatabasename' 
    AND `TABLE_NAME`='yourtablename';

It's VERY powerful, and can give you TONS of information without need to parse text (Such as column type, whether the column is nullable, max column size, character set, etc)...

Oh, and it's standard SQL (Whereas SHOW ... is a MySQL specific extension)...

For more information about the difference between SHOW... and using the INFORMATION_SCHEMA tables, check out the MySQL Documentation on INFORMATION_SCHEMA in general...

Answer 6

if you only need the field names and types (perhaps for easy copy-pasting into Excel):

SELECT COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA='databasenamegoeshere'
AND DATA_TYPE='decimal' and TABLE_NAME = 'tablenamegoeshere'

remove

DATA_TYPE='decimal'

if you want all data types