CODEWITHSUNDEEP
phpsqlmysql
EnglishAdam
EnglishAdam

Reputation: 1390

How to SELECT DEFAULT value of a field

I can't seem to find or write a sqlquery that SELECTS the DEFAULT VALUE

(and I don't think I can generate it in phpmyadmin for me to copy)

I tried to SELECT it as if it was a record but to no avail...

 $defaultValue_find = mysql_query(
         "SELECT $group FROM grouptable WHERE $group='DEFAULT'")  
      or die("Query failed:".mysql_error());
 $defaultValue_fetch = mysql_fetch_row($defaultValue_find);
 $defaultValue = $defaultValue_fetch[0];
 echo $defaultValue;

Upvotes: 9

Views: 9615

Answers (3)

ypercubeᵀᴹ
ypercubeᵀᴹ

Reputation: 115530

"SELECT $group FROM grouptable WHERE $group=DEFAULT( $group ) "

Or I think better:

"SELECT DEFAULT( $group ) FROM grouptable LIMIT 1 "

The above will only work if there is at least 1 row in grouptable. If you want the result even if the grouptable has no rows, you can use this:

"SELECT DEFAULT( $group ) 
 FROM (SELECT 1) AS dummy
   LEFT JOIN grouptable 
     ON True
 LIMIT 1 ;"

Upvotes: 12

HoldOffHunger
HoldOffHunger

Reputation: 20881

You can get the default column of any table, and in fact lots of interesting information about it, by looking at the INFORMATION_SCHEMA.COLUMNS tables. As the documentation states...

INFORMATION_SCHEMA provides access to database metadata, information about the MySQL server such as the name of a database or table, the data type of a column, or access privileges. (Source: MySQL 8.0 Reference Manual / INFORMATION_SCHEMA Tables / Introduction.)

So, to get the column default, just SELECT COLUMN_DEFAULT, like...

SELECT COLUMN_DEFAULT
FROM information_schema.columns
WHERE TABLE_SCHEMA = 'YourSchema'
AND TABLE_NAME = 'YourTable' AND 
COLUMN_NAME = 'YourField';

You can then just wrap this into a subquery, SELECT * FROM YourTable WHERE YourField = (queryabove). This lets you make a much more customizable, default-based list in your MySQL query.

Upvotes: 1

vess
vess

Reputation: 523

Get the default values of all fields in mytable in the associative array $res:

// MySQL v.5.7+
$res = [];
$sql = "SHOW FULL COLUMNS FROM `mytable`";
foreach ($PDO->query( $sql, PDO::FETCH_ASSOC ) as $row) {
    $res[$row['Field']] = $row['Default'] ;
}
print_r($res);

Upvotes: 0

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