a MYSQL script to convert the column names to lowercase

Question

I am looking for a single MYSQL script to convert ALL column names in a database to lowercase in one go...

I have inherited a MYSQL database that has a lot of mixed case column names (150 tables with a strange naming convention) and I don't want to go through manually each table by table to do this.

Has anyone got such a script?

Thanks

Answer 1

You can solve this task by building a script, starting with the output from this statement:

SELECT table_name, column_name, data_type
FROM information_schema.columns
WHERE table_schema = 'dbname';
ORDER BY table_name

Details about this feature can be found here "MYSQL::The INFORMATION_SCHEMA COLUMNS Table"

Then you can use the ALTER TABLE .. CHANGE feature to change the name of the columns

e.g.

ALTER TABLE mytable CHANGE old_name new_name varchar(5);

See also "MYSQL::ALTER TABLE Syntax"

Different datatype have different requirements so you need the UNIONs:

SELECT 'ALTER TABLE '||table_name||' CHANGE '|| column_name||' '||lower(column_name)||' '||datatype||'('||CHAR(character_maximum_length)||');' AS Line
    FROM information_schema.columns
    WHERE table_schema = dbname and datatype in ( 'CHAR', 'VARCHAR' )
    ORDER BY table_name
    UNION
SELECT 'ALTER TABLE '||table_name||' CHANGE '|| column_name||' '||lower(column_name)||' '||datatype||'('||CHAR(numeric_precision)||');' AS Line
    FROM information_schema.columns
    WHERE table_schema = dbname and datatype in ( 'INTEGER' )
    ORDER BY table_name
    UNION
SELECT 'ALTER TABLE '||table_name||' CHANGE '|| column_name||' '||lower(column_name)||' '||datatype||'('||CHAR(numeric_precision)||','||CHAR(numeric_scale)|');' AS Line
    FROM information_schema.columns
    WHERE table_schema = dbname and datatype in ( 'FLOAT' )
    ORDER BY table_name
    UNION
SELECT 'ALTER TABLE '||table_name||' CHANGE '|| column_name||' '||lower(column_name)||' '||datatype||');' AS Line
    FROM information_schema.columns
    WHERE table_schema = dbname and datatype in ( 'DATE' )
    ORDER BY table_name

Answer 2

In case anybody else wants this below is an example of the completed query, please test before you use.....

EDIT COMPLETED SOLUTION AS REQUESTED

SELECT CONCAT(
'ALTER TABLE ', table_name, 
' CHANGE ', column_name, ' ', 
LOWER(column_name), ' ', column_type, ' ', extra,
CASE WHEN IS_NULLABLE = 'YES' THEN  ' NULL' ELSE ' NOT NULL' END, ';') AS line
FROM information_schema.columns
WHERE table_schema = '<DBNAME>' 
AND data_type IN ('char', 'varchar','INT', 'TINYINT', 'datetime','text','double','decimal')
ORDER BY line;

HTH somebody in the future... BTW views are also scripted here so you may need to take them out of your final SQL code

Answer 3

You can rename all table and column names to lowercase by applying the following regular expression to a SQL dump (for example, the dump generated by mysqldump):

s/`\(\w\+\)`/\L&/g

This works because all table and column names are wrapped by `` (backticks). It is better to do this on the schema only, separate from the data (work with table structures only and then do the inserts).

To do this in Vim, open the SQL dump and enter the following command:

:%s/`\(\w\+\)`/\L&/g

Or do it from the command line using sed:

sed 's/`\(\w\+\)`/\L&/g' input.sql > output.sql

If you need to do it repeatedly, store the expression in a text file, and invoke it as follows:

sed -f regex.txt input.sql > output.sql

Answer 4

The solution proposed by lepe is really the only safe way to go. The scripting methods are too dangerous, easy to export or process the wrong data definition. All of the example scripts above leave out several data types, so they are incomplete.

I did a sqldump which places backticks around the table and column names, then used Notepad++ to Search on (`.*`) and Replace With \L\1. That rendered all of my table and column names to lower case.

Then I backed up my database, wiped out all of the tables and then executed my .sql file to rebuild. I did not worry about doing structure separate from data as I found no occurances of the backtick symbol in any of my data.

In my case, I need my column names all lower case because my development environment automatically converts first_name to First Name: as my field label for data entry. If I left them as caps (which I inherited), they would convert to FIRST NAME which is not what I want, I'd have to alter all of my field labels.