Laravel + mysql：可以创建/更新临时表，但不能从以下项中选择：

Question

I can create a temporary table, but then when I try to select from it it says the table doesn't exist. I figure its because DB::statement and DB::select have somehow got a different session with the database but I'm not sure how to fix it.

How can I create a temporary table, insert into it, and select from it, in the same script?

Below is output from tinker which demonstrates the issue:

DB::select("select count(*) from users"); //12
DB::statement("create temporary table tempUsers like users"); //true
DB::statement("insert into tempUsers (id,email) VALUES (1, 'joe@example.com')"); //true

doesnt seem to exist on "select" session

DB::select("select count(*) from tempUsers"); 

Illuminate\\Database\\QueryException with message 'SQLSTATE[42S02]: Base table or view not found: 1146 Table 'db.tempUsers' doesn't exist (SQL: select count(*) from tempUsers)'

still exists on "statement" session

DB::statement("insert into tempUsers (id,email) VALUES (2, 'bob@example.com')"); //true
DB::statement("insert into tempUsers (id,email) VALUES (1, 'joe@example.com')"); 

Illuminate\\Database\\QueryException with message 'SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1' for key 'PRIMARY' (SQL: INSERT INTO tempUsers (id,email) VALUES (1,'bob@example.com'))'

I get identical behavior using $table->temporary() with Blueprint , ie

Schema::create('tempTable',function ($table) {$table->increments('id');
    $table->timestamps();
    $table->temporary();
}); 

Using Laravel 5.4, MySQL 5.6

I can manipulate and select from temp tables just fine when I am connected to the DB outside of laravel

Answer 1

If you create temp table inside stored procedure it gets destroyed once the stored procedure is completed.

Scope of the temporary table is important, visible only to the particular user. Temporary tables begin with a pound symbol '#' or '@' very important as it seems that you have missed that part.

So if you tweak your migration to:

Schema::create('#tmpTest', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
});

Then run:

php artisan migrate:fresh

To insert data on temp table:

\\DB::statement("insert into #tmpTest (id,name) VALUES (1, 'joe@example.com')");

To fetch those data using select:

$a = DB::select('select * from #tmpTest '); dd($a);

It gives me the result:

Answer 2

Turns out the issue is caused by our reader-writer set up. We use one database for writes, and another for reads. The writer database is replicated to the read database, but the temp table is not replicated , since its a temp table and its locked to the current session with the writer.

If using Laravel 5.5+, the solution is to set 'sticky' => true on the database connection. This makes the writer get treated as the reader after any writes, to bypass the issue of replication delay.

Since I am stick on Laravel 5.4 for now, my solution was to create a standard table, but treat it like a temp table and drop it at the end of the method.

DB::select("select count(*) from users"); //12

//use uniqid to ensure a unique tablename since it is now in the global namespace
$tableName=uniqid('tempUsers'); 

DB::unprepared("create table $tableName like users"); //true
DB::statement("insert into tempUsers (id,email) VALUES (1, 'joe@example.com')"); //true
DB::select("select count(*) from $tableName"); //1
//...do stuff with temp table
//...
Schema::drop($tableName);
// return