+=item sql_h_searchs END_TIMESTAMP [ START_TIMESTAMP ]
+
+Like sql_h_search, but limited to the single most recent record (before
+END_TIMESTAMP)
+
+=cut
+
+sub sql_h_searchs {
+ my $self = shift;
+ my($select, $where, $cacheobj, $as) = $self->sql_h_search(@_);
+ $where .= ' LIMIT 1';
+ ($select, $where, $cacheobj, $as);
+}
+
+=item sql_diff START_TIMESTAMP, END_TIMESTAMP[, WHERE]
+
+Returns a complete SQL statement to find all records that were changed
+between START_TIMESTAMP and END_TIMESTAMP. This finds only replacements,
+not new or deleted records.
+
+For each modified record, this will return I<one> row (not two rows as in
+the history table) with the primary key of the record, "old_historynum"
+(the historynum of the last modification before START_TIMESTAMP), and
+"new_historynum" (the last modification before END_TIMESTAMP). Join these
+back to the h_* table to retrieve the actual field values.
+
+Within the query, the last history records as of START and END are aliased
+as "old" and "new"; you can append a WHERE clause to take advantage of this.
+
+=cut
+
+sub sql_diff {
+ my $class = shift;
+ my $table = $class->table;
+ my ($real_table) = ($table =~ /^h_(\w+)$/);
+ my $pkey = dbdef->table($real_table)->primary_key;
+ my @fields = "FS::$real_table"->fields;
+
+ my ($sdate, $edate) = @_;
+ ($sdate, $edate) = ($edate, $sdate) if $edate < $sdate;
+
+ my @select = (
+ "old.$pkey",
+ 'old.historynum AS old_historynum',
+ 'new.historynum AS new_historynum',
+ );
+ my $new =
+ "SELECT DISTINCT ON ($pkey) * FROM $table
+ WHERE history_action = 'replace_new'
+ AND history_date >= $sdate AND history_date < $edate
+ ORDER BY $pkey ASC, history_date DESC";
+ my $old =
+ "SELECT DISTINCT ON ($pkey) * FROM $table
+ WHERE (history_action = 'replace_new' OR history_action = 'insert')
+ AND history_date < $sdate
+ ORDER BY $pkey ASC, history_date DESC";
+
+ my $from = "($new) AS new JOIN ($old) AS old USING ($pkey)";
+
+ return "SELECT ".join(',', @select)." FROM $from";
+}
+
+