System.Data.SQLite

or in a USING or ON clause that is of the form

<blockquote>
     column  OP  EXPR
</blockquote>

<p>Where "column" is a column in the virtual table, OP is an operator 
like "=" or "<", and EXPR is an arbitrary expression. So, for example,
like "=" or "&lt;", and EXPR is an arbitrary expression. So, for example,
if the WHERE clause contained a term like this:

<blockquote><pre>
     a = 5
</pre></blockquote>

<p>Then one of the constraints would be on the "a" column with 
operator "=" and an expression of "5". Constraints need not have a
literal representation of the WHERE clause. The query optimizer might
make transformations to the 
WHERE clause in order to extract as many constraints 
as it can. So, for example, if the WHERE clause contained something 
like this:

<blockquote><pre>
     x BETWEEN 10 AND 100 AND 999>y
     x BETWEEN 10 AND 100 AND 999&gt;y
</pre></blockquote>

<p>The query optimizer might translate this into three separate constraints:

<blockquote><pre>
     x >= 10
     x <= 100
     y < 999
     x &gt;= 10
     x &lt;= 100
     y &lt; 999
</pre></blockquote>

<p>For each constraint, the aConstraint[].iColumn field indicates which 
column appears on the left-hand side of the constraint.
The first column of the virtual table is column 0. 
The rowid of the virtual table is column -1. 
The aConstraint[].op field indicates which operator is used.