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    <p><strong>Safe</strong> </p> <pre><code>query.SQL.Text := 'select * from table_name where name=:Name'; </code></pre> <p>This code is safe because you are using parameters.<br> Parameters are always safe from SQL-injection.</p> <p><strong>Unsafe</strong></p> <pre><code>var Username: string; ... query.SQL.Text := 'select * from table_name where name='+ UserName; </code></pre> <p>Is unsafe because Username could be <code>name; Drop table_name;</code> Resulting in the following query being executed.</p> <pre><code>select * from table_name where name=name; Drop table_name; </code></pre> <p>Also <strong>Unsafe</strong></p> <pre><code>var Username: string; ... query.SQL.Text := 'select * from table_name where name='''+ UserName+''''; </code></pre> <p>Because it if username is <code>' or (1=1); Drop Table_name; --</code> It will result in the following query:</p> <pre><code>select * from table_name where name='' or (1=1); Drop Table_name; -- ' </code></pre> <p><strong>But this code is safe</strong></p> <pre><code>var id: integer; ... query.SQL.Text := 'select * from table_name where id='+IntToStr(id); </code></pre> <p>Because <code>IntToStr()</code> will only accept integers so no SQL code can be injected into the query string this way, only numbers <em>(which is exactly what you want and thus allowed)</em></p> <p><strong>But I want to do stuff that can't be done with parameters</strong></p> <p>Parameters can only be used for values. They cannot replace field names or table names. So if you want to execute this query</p> <pre><code>query:= 'SELECT * FROM :dynamic_table '; {doesn't work} query:= 'SELECT * FROM '+tableName; {works, but is unsafe} </code></pre> <p>The first query fails because you cannot use parameters for table or field names.<br> The second query is unsafe but is the only way this this can be done.<br> How to you stay safe? </p> <p>You have to check the string <code>tablename</code> against a list of approved names. </p> <pre><code>Const ApprovedTables: array[0..1] of string = ('table1','table2'); procedure DoQuery(tablename: string); var i: integer; Approved: boolean; query: string; begin Approved:= false; for i:= lo(ApprovedTables) to hi(ApprovedTables) do begin Approved:= Approved or (lowercase(tablename) = ApprovedTables[i]); end; {for i} if not Approved then exit; query:= 'SELECT * FROM '+tablename; ... </code></pre> <p>That's the only way to do this, that I know of.</p> <p><strong>BTW Your original code has an error:</strong></p> <pre><code>query.SQL.Text := 'select * from table_name where name=:Name where id=:ID'; </code></pre> <p>Should be </p> <pre><code>query.SQL.Text := 'select * from table_name where name=:Name and id=:ID'; </code></pre> <p>You cannot have two <code>where</code>'s in one (sub)query</p>
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    1. PODelphi - prevent against SQL injection
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    1. USJohan
    1. USJohan
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    1. PODelphi - prevent against SQL injection
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      1. VTUpMod
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    1. COthank you Johan. I have corrected the question.+1
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      1. USRBA
    2. CO+1 for covering multiple scenarios
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      1. USAdrian Carneiro
    3. COBut still you can inject SQL parameter with `name; Drop table_name;` if it's entered by user in such kind of input box
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