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+[h1]SQL Conventions[/h1]
+[b]Intro[/b]
+The following common SQL conventions appear throughout the code in many places. We use a simple DBA (DataBase Abstraction layer) to handle differences between databases. Please be sure to use only standards-compliant SQL.
+
+[b]Rule One[/b]
+Worth Repeating: Don't use non-standard SQL. This goes for addons as well. If you do use non-standard SQL, and the dba funcs are insufficient, do a if()/switch() or similar for all currently supported databases. Currently nothing red# does requires non-standard SQL.
+
+[b]Using a format string[/b]
+[li]Uses sprintf()
+To be written
+[code]// Example
+$r = q("SELECT * FROM profile WHERE uid = %d",
+	local_channel()
+);
+[/code][/li]
+
+[b]Checking bit flags in a where clause[/b]
+[li]You must explicitly convert integers to booleans. The easiest way to do this is to compare to 0.
+[code]// Example
+$r = q("SELECT abook_id, abook_flags, abook_my_perms, abook_their_perms, xchan_hash, xchan_photo_m, xchan_name, xchan_url from abook left join xchan on abook_xchan = xchan_hash where abook_channel = %d and not (abook_flags & %d)>0 ",
+	intval($uid),
+	intval(ABOOK_FLAG_SELF)
+);
+[/code]
+[/li]
+[li]Turning off a flag
+[code]$y = q("update xchan set xchan_flags = (xchan_flags & ~%d) where (xchan_flags & %d)>0 and xchan_hash = '%s'",
+	intval(XCHAN_FLAGS_ORPHAN),
+	intval(XCHAN_FLAGS_ORPHAN),
+	dbesc($rr['hubloc_hash'])
+);[/code]
+[/li]
+[li]Turning on a flag
+[code]$y = q("update xchan set xchan_flags = (xchan_flags | %d) where xchan_hash = '%s'",
+	intval(XCHAN_FLAGS_ORPHAN),
+	dbesc($rr['hubloc_hash'])
+);[/code]
+[/li]
+
+[b]Using relative times (INTERVALs)[/b]
+[li]Sometimes you want to compare something, like less than x days old.
+[code]// Example
+$r = q("SELECT * FROM abook left join xchan on abook_xchan = xchan_hash 
+	WHERE abook_dob > %s + interval %s and abook_dob < %s + interval %s",
+	db_utcnow(), db_quoteinterval('7 day'),
+	db_utcnow(), db_quoteinterval('14 day')
+);[/code]
+[/li]
+[b]Paged results[/b]
+[li]To be written
+[code]// Example
+$r = q("SELECT * FROM mail WHERE uid=%d AND $sql_extra ORDER BY created DESC LIMIT %d OFFSET %d",
+	intval(api_user()),
+	intval($count), intval($start)
+);[/code][/li]
+
+[b]NULL dates[/b]
+[li]To be written
+[code]// Example
+$r = q("DELETE FROM mail WHERE expires != '%s' AND expires < %s ",
+	dbesc(NULL_DATE),
+	db_utcnow()
+);[/code][/li]
+
+[b]Storing binary data[/b]
+[li]To be written
+[code]// Example
+$x = q("update photo set data = '%s', height = %d, width = %d where resource_id = '%s' and uid = %d and scale = 0",
+	dbescbin($ph->imageString()),
+	intval($height),
+	intval($width),
+	dbesc($resource_id),
+	intval($page_owner_uid)
+);[/code][/li]
+
+[b]Current timestamp[/b]
+[li][code]// Example
+$randfunc = db_getfunc('rand');
+$r = q("select xchan_url from xchan left join hubloc on hubloc_hash = xchan_hash where hubloc_connected > %s - interval %s order by $randfunc limit 1",
+	db_utcnow(), db_quoteinterval('30 day')
+);[/code][/li]
+
+[b]SQL Function and Operator Abstraction[/b]
+[li]Sometimes the same function or operator has a different name/symbol in each database. You use db_getfunc('funcname') to look them up. The string is [i]not[/i] case-sensitive; do [i]not[/i] include parens.
+[code]// Example
+$randfunc = db_getfunc('rand');
+$r = q("select xchan_url from xchan left join hubloc on hubloc_hash = xchan_hash where hubloc_connected > %s - interval %s order by $randfunc limit 1",
+	db_utcnow(), db_quoteinterval('30 day')
+);[/code][/li]
+
+#include doc/macros/main_footer.bb;
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