BP_Activity_Query::get_sql_for_clause( array $clause, array $parent_query )

	protected function get_sql_for_clause( $clause, $parent_query ) {
		global $wpdb;

		$sql_chunks = array(
			'where' => array(),
			'join' => array(),
		);

		$column = isset( $clause['column'] ) ? $this->validate_column( $clause['column'] ) : '';
		$value  = isset( $clause['value'] )  ? $clause['value'] : '';
		if ( empty( $column ) || ! isset( $clause['value'] ) ) {
			return $sql_chunks;
		}

		if ( isset( $clause['compare'] ) ) {
			$clause['compare'] = strtoupper( $clause['compare'] );
		} else {
			$clause['compare'] = isset( $clause['value'] ) && is_array( $clause['value'] ) ? 'IN' : '=';
		}

		// Default 'compare' to '=' if no valid operator is found.
		if ( ! in_array( $clause['compare'], array(
			'=', '!=', '>', '>=', '<', '<=',
			'LIKE', 'NOT LIKE',
			'IN', 'NOT IN',
			'BETWEEN', 'NOT BETWEEN',
			'REGEXP', 'NOT REGEXP', 'RLIKE'
		) ) ) {
			$clause['compare'] = '=';
		}

		$compare = $clause['compare'];

		$alias = ! empty( $this->table_alias ) ? "{$this->table_alias}." : '';

		// Next, Build the WHERE clause.
		$where = '';

		// Value.
		if ( isset( $clause['value'] ) ) {
			if ( in_array( $compare, array( 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN' ) ) ) {
				if ( ! is_array( $value ) ) {
					$value = preg_split( '/[,\s]+/', $value );
				}
			}

			// Tinyint.
			if ( ! empty( $column ) && true === in_array( $column, array( 'hide_sitewide', 'is_spam' ) ) ) {
				$sql_chunks['where'][] = $wpdb->prepare( "{$alias}{$column} = %d", $value );

			} else {
				switch ( $compare ) {
					// IN uses different syntax.
					case 'IN' :
					case 'NOT IN' :
						$in_sql = BP_Activity_Activity::get_in_operator_sql( "{$alias}{$column}", $value );

						// 'NOT IN' operator is as easy as a string replace!
						if ( 'NOT IN' === $compare ) {
							$in_sql = str_replace( 'IN', 'NOT IN', $in_sql );
						}

						$sql_chunks['where'][] = $in_sql;
						break;

					case 'BETWEEN' :
					case 'NOT BETWEEN' :
						$value = array_slice( $value, 0, 2 );
						$where = $wpdb->prepare( '%s AND %s', $value );
						break;

					case 'LIKE' :
					case 'NOT LIKE' :
						$value = '%' . bp_esc_like( $value ) . '%';
						$where = $wpdb->prepare( '%s', $value );
						break;

					default :
						$where = $wpdb->prepare( '%s', $value );
						break;

				}
			}

			if ( $where ) {
				$sql_chunks['where'][] = "{$alias}{$column} {$compare} {$where}";
			}
		}

		/*
		 * Multiple WHERE clauses should be joined in parentheses.
		 */
		if ( 1 < count( $sql_chunks['where'] ) ) {
			$sql_chunks['where'] = array( '( ' . implode( ' AND ', $sql_chunks['where'] ) . ' )' );
		}

		return $sql_chunks;
	}