mysql - Query Two Tables - but not trying to JOIN? -


i have 2 tables have identical columns. first table contains "current" state of particular record , second table contains previous stats of records (it's history table). second table has fk first table.

i'd query both tables entire records history, including current state in 1 result. don't think join i'm trying "joins" multiple tables "horizontally" (one or more columns of 1 table combined 1 or more columns of table produce result includes columns both tables). rather, i'm trying "join"(???) tables "vertically" (meaning, no columns getting added result, results both tables falling under same columns in result set).

not sure if i'm expressing make sense -- or if it's possible in mysql.

to accomplish this, use union between 2 select statements. suggest selecting derived table in following manner can sort columns in result set. suppose wanted combine results following 2 queries:

select fielda, fieldb table1; select fieldx, fieldy table2;

we join these union statement follows:

select field1, field2 (     select fielda `field1`, fieldb `field2` table1      union select fieldx `field1`, fieldy `field2` table2)  `derived_table`  order field1 asc, field2 desc

in example, have selected table1 , table2 fields similar, not identically named, sharing same data type. matched using aliases (e.g., fielda in table1 , fieldx in table2 both map field1 in result set, etc.).

if each table has same column names, field aliasing not required, , query becomes simpler.

note: in mysql necessary name derived tables, if name given not intended used.


Comments

Post a Comment

Popular posts from this blog

javascript - jQuery: Add class depending on URL in the best way -

i have html progress meter: <div class="col-md-3" style="margin-left: -20px;"> <div class="progress-pos active" id="progess-1"> <div class="progress-pos-inner"> login </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-2"> <div class="progress-pos-inner"> scan items </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-3"> <div class="progress-pos-inner"> confirm address </div> </div> </div> <div class="col-md-3 progress-pos-container"> <div class="progress-pos" id="progess-4"> <div class="progress-pos-in
Read more

caching - How to check if a url path exists in the service worker cache -

i need check if particular url path exists in service worker cache. example, suppose url is: /myserviceworker/service?a=110&b=70 this url exists in cache, there many of them different values of , b. now, suppose want refresh of these urls, how can that? i want know how access key values service worker cache. if know key, plan follows: var url = new url(key); if(url.pathname === "\/myserviceworker/service") refetch key but not sure how cache key , in format is. mean, string or url? cache api has match() method returns promise resolving in response object if match or undefined if no match exists. second parameter object can specify ignoresearch not take account url parameters. the ignoresearch option supported firefox ( chrome status here ). in other hand, retrieve cache entries, can use keys() method.
Read more

Redirect to a HTTPS version using .htaccess -

i need modify .htaccess file redirect urls https version without "www". http://example.com --> https://example.com http://www.example.com --> https://example.com https://www.example.com --> https://example.com this how .htaccess file looks like: rewriteengine on rewritecond %{request_filename} !-d rewritecond %{request_filename} !-f rewriterule ^(.*)$ redirect.php?id=$1&page=$2 [qsa,l] what modifications need make .htaccess in order forward https without "www"? it depends on doing current code. looks file called redirect trying display php page seo friendly url. think might confusing people. anyway, need , force https without www, need 1 more rule above. also second rule needs two capture groups in rewriterule test string because wanting 2 different values using $1 , $2 references. rewriteengine on #rediect www non www and/or http https --- combinations. rewritecond %{http_host} !^example\.com [nc,or] rewritecond %{https} !^
Read more