Prado\Data\Common\Mssql\TMssqlCommandBuilder::applyLimitOffset PHP Method

TMssqlCommandBuilder Class Documentation Show file Open project: pradosoft/prado

applyLimitOffset() public method

The idea for limit with offset is done by modifying the sql on the fly with numerous assumptions on the structure of the sql string. The modification is done with reference to the notes from http://troels.arvin.dk/db/rdbms/#select-limit-offset


SELECT * FROM (
 SELECT TOP n * FROM (
   SELECT TOP z columns      -- (z=n+skip)
   FROM tablename
   ORDER BY key ASC
 ) AS FOO ORDER BY key DESC -- ('FOO' may be anything)
) AS BAR ORDER BY key ASC    -- ('BAR' may be anything)

Regular expressions are used to alter the SQL query. The resulting SQL query may be malformed for complex queries. The following restrictions apply

In particular, commas should NOT be used as part of the ordering expression or identifier. Commas must only be used for separating the ordering clauses.
In the ORDER BY clause, the column name should NOT be be qualified with a table name or view name. Alias the column names or use column index.
No clauses should follow the ORDER BY clause, e.g. no COMPUTE or FOR clauses.

public applyLimitOffset ( $sql, $limit, $offset ) : string
return	string	SQL with limit and offset.

    public function applyLimitOffset($sql, $limit = -1, $offset = -1)
    {
        $limit = $limit !== null ? intval($limit) : -1;
        $offset = $offset !== null ? intval($offset) : -1;
        if ($limit > 0 && $offset <= 0) {
            //just limit
            $sql = preg_replace('/^([\\s(])*SELECT( DISTINCT)?(?!\\s*TOP\\s*\\()/i', "\\1SELECT\\2 TOP {$limit}", $sql);
        } else {
            if ($limit > 0 && $offset > 0) {
                $sql = $this->rewriteLimitOffsetSql($sql, $limit, $offset);
            }
        }
        return $sql;
    }

TMssqlCommandBuilder

applyLimitOffset

findOrdering

getLastInsertID

joinOrdering

reverseDirection

rewriteLimitOffsetSql