Prepend text to MySQL columns' names
mysql
Solution
You can use the INFORMATION_SCHEMA.COLUMNS table to formulate the query and then use dynamic SQL to execute it.
First let's make a sample database called `dotancohen` and a table called `mytable`
mysql> drop database if exists dotancohen;
Query OK, 1 row affected (0.03 sec)
mysql> create database dotancohen;
Query OK, 1 row affected (0.00 sec)
mysql> use dotancohen
Database changed
mysql> create table mytable
-> (
-> id int not null auto_increment,
-> username varchar(30),
-> realname varchar(30),
-> primary key (id)
-> );
Query OK, 0 rows affected (0.06 sec)
mysql> insert into mytable (realname,username) values
-> ('rolando','odnalor'),('pamela','alemap'),
-> ('dominique','euqinimod'),('diamond','dnomaid');
Query OK, 4 rows affected (0.05 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql> select * from mytable;
+----+-----------+-----------+
| id | username | realname |
+----+-----------+-----------+
| 1 | odnalor | rolando |
| 2 | alemap | pamela |
| 3 | euqinimod | dominique |
| 4 | dnomaid | diamond |
+----+-----------+-----------+
4 rows in set (0.00 sec)
mysql>
Here is the metadata table called INFORMATION_SCHEMA.COLUMNS:
mysql> desc INFORMATION_SCHEMA.COLUMNS;
+--------------------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------------------+---------------------+------+-----+---------+-------+
| TABLE_CATALOG | varchar(512) | NO | | | |
| TABLE_SCHEMA | varchar(64) | NO | | | |
| TABLE_NAME | varchar(64) | NO | | | |
| COLUMN_NAME | varchar(64) | NO | | | |
| ORDINAL_POSITION | bigint(21) unsigned | NO | | 0 | |
| COLUMN_DEFAULT | longtext | YES | | NULL | |
| IS_NULLABLE | varchar(3) | NO | | | |
| DATA_TYPE | varchar(64) | NO | | | |
| CHARACTER_MAXIMUM_LENGTH | bigint(21) unsigned | YES | | NULL | |
| CHARACTER_OCTET_LENGTH | bigint(21) unsigned | YES | | NULL | |
| NUMERIC_PRECISION | bigint(21) unsigned | YES | | NULL | |
| NUMERIC_SCALE | bigint(21) unsigned | YES | | NULL | |
| CHARACTER_SET_NAME | varchar(32) | YES | | NULL | |
| COLLATION_NAME | varchar(32) | YES | | NULL | |
| COLUMN_TYPE | longtext | NO | | NULL | |
| COLUMN_KEY | varchar(3) | NO | | | |
| EXTRA | varchar(27) | NO | | | |
| PRIVILEGES | varchar(80) | NO | | | |
| COLUMN_COMMENT | varchar(1024) | NO | | | |
+--------------------------+---------------------+------+-----+---------+-------+
19 rows in set (0.02 sec)
mysql>
What you need from this table are the following columns:
- table_schema
- table_name
- column_name
- ordinal_position
What you are asking for is to have the column_name and the column_name prepended with `a_`
Here is the query and how to execute it:
select concat('select ',column_list,' from ',dbtb) into @newsql
from (select group_concat(concat(column_name,' a_',column_name)) column_list,
concat(table_schema,'.',table_name) dbtb from information_schema.columns
where table_schema = 'dotancohen' and table_name = 'mytable'
order by ordinal_position) A;
select @newsql;
prepare stmt from @newsql;
execute stmt;
deallocate prepare stmt;
Let's execute it
mysql> select concat('select ',column_list,' from ',dbtb) into @newsql
-> from (select group_concat(concat(column_name,' a_',column_name)) column_list,
-> concat(table_schema,'.',table_name) dbtb from information_schema.columns
-> where table_schema = 'dotancohen' and table_name = 'mytable'
-> order by ordinal_position) A;
Query OK, 1 row affected (0.01 sec)
mysql> select @newsql;
+--------------------------------------------------------------------------------+
| @newsql |
+--------------------------------------------------------------------------------+
| select id a_id,username a_username,realname a_realname from dotancohen.mytable |
+--------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> prepare stmt from @newsql;
Query OK, 0 rows affected (0.00 sec)
Statement prepared
mysql> execute stmt;
+------+------------+------------+
| a_id | a_username | a_realname |
+------+------------+------------+
| 1 | odnalor | rolando |
| 2 | alemap | pamela |
| 3 | euqinimod | dominique |
| 4 | dnomaid | diamond |
+------+------------+------------+
4 rows in set (0.01 sec)
mysql> deallocate prepare stmt;
Query OK, 0 rows affected (0.00 sec)
mysql>
Give it a Try !!!
You mentioned in your question : The SELECT username AS a_username format will not help as I need to continue using the * field selection.
All you have to do to implement my suggestion is run the query using tableA as follows:
select concat('select ',column_list,' from ',dbtb) into @newsql
from (select group_concat(concat(column_name,' a_',column_name)) column_list,
concat(table_schema,'.',table_name) dbtb from information_schema.columns
where table_schema = DATABASE() and table_name = 'tableA'
order by ordinal_position) A;
When you retrieve that query result, just use it as the query to submit to mysql_query.
Problem
Supposing a query such as: ``` SELECT * FROM tableA; ``` How can I prepend `a_` to each columns' name? For example if there is a column "username" it would be accessed in the results as "a_username". EDIT: The `SELECT username AS a_username` format will not help as I need to continue using the `*` field selection. There is a JOIN and a potential conflict with a returned column from another table in the JOIN. I will be iterating over the returned columns (foreach) and only want to output the columns that came from a particular table (whose schema may change) to HTML input fields where a site admin could edit the fields' content directly. The SQL query in question looks like `SELECT firstTable.*, anotherTable.someField, anotherTable.someOtherField` and their exists the possibility that someField or someOtherField exists in firstTable. Thanks.