Wildcards in column name for MySQL

Question

I am trying to select multiple columns, but not all of the columns, from the database. All of the columns I want to select are going to start with \"word\".

So in ps

Answer 1

No, SQL doesn't provide you with any syntax to do such a select.

What you can do is ask MySQL for a list of column names first, then generate the SQL query from that information.

SELECT column_name
FROM information_schema.columns
WHERE table_name = 'your_table'
    AND column_name LIKE 'word%'

let's you select the column names. Then you can do, in Python:

"SELECT * FROM your_table WHERE " + ' '.join(['%s = 1' % name for name in columns])

Instead of using string concatenation, I would recommend using SQLAlchemy instead to do the SQL generating for you.

However, if all you are doing is limit the number of columns there is no need to do a dynamic query like this at all. The hard work for the database is selecting the rows; it makes little difference to send you 5 columns out of 10, or all 10.

In that case just use a "SELECT * FROM ..." and use Python to pick out the columns from the result set.

Answer 2

No, you cannot dynamically produce the list of columns to be selected. It will have to be hardcoded in your final query.

Your current query would produce a result set with one column and the value of that column would be the string "word%" in all rows that satisfy the condition.

Answer 3

You can generate the list of column names first by using

SHOW COLUMNS IN tblname LIKE "word%"

Then loop through the cursor and generate SQL statement uses all the columns from the query above.

"SELECT {0} FROM searchterms WHERE onstate = 1".format(', '.join(columns))

Answer 4

This could be helpful: MySQL wildcard in select

In conclusion it is not possible in MySQL directly.

What you could do as a dirty workaround is get all the column names from the table with an initial query (http://dev.mysql.com/doc/refman/5.0/en/show-columns.html) and then compare in python if the name matches your pattern. Afterwards you could do the MySQL select statement with the found column names like this:

SELECT word1, word2, word3 from searchterms where onstate = 1;