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Am trying to fetch data using two conditions and then use descending order in mysql query , can anyone help ?

What I have tried:

'select * from mc_chat_messages where n_cent="'.$cent.'" and date="'.$date.'" order by ch_id desc';
Posted
Updated 11-Jan-21 21:58pm
Comments
Sandeep Mewara 12-Jan-21 3:55am
   
Not sure of what is the query here?

1 solution

1) Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'
Which SQL sees as three separate commands:
SQL
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
SQL
DROP TABLE MyTable;
A perfectly valid "delete the table" command
SQL
--'
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

2) DATE is a MySQL keyword and should not be used as a column name: "InsertDate", or "EnterDate" is usable, but "Date" on it's own will cause errors unless the column name is escaped.

Fix those two throughout your app, and your problem will probably go away at the same time.
   

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