SQL查询找到表名

Question

I have 5 different tables in my dB with the structure Name|Price|Id..

I have a unique price and Id entry combination.

Using these 2, what could be the possible SQL query to fetch the name of the table in which this entry is present?

I need to fetch the name of this table in order to update the value of Price.

Answer 1

You really should normalise your database properly and use a single table, but if you really need a kludge then:

SELECT name, brand, id, 'Tea' as tablename
  FROM TableTea
 WHERE brand = 'abc'
   AND id = 100
UNION
SELECT name, brand, id, 'Coffee' as tablename
  FROM TableCoffee
 WHERE brand = 'abc'
   AND id = 100
UNION
SELECT name, brand, id, 'Chocolate' as tablename
  FROM TableChocolate
 WHERE brand = 'abc'
   AND id = 100

And you'll have to change it if you ever add new products

Answer 2

if your DBMS is MySQL you can use this Query:

SELECT Result.TABLE_NAME FROM (
  SELECT  TABLE_NAME,COLUMN_NAME,COUNT(*) AS QTA FROM INFORMATION_SCHEMA.COLUMNS  
  where  TABLE_SCHEMA = 'NAME_DB'
  and COLUMN_NAME IN ('Name','Price','Id')
  GROUP BY TABLE_NAME
 ) as Result
WHERE Result.QTA = 3

i have already tried to do without php

Replace NAME_DB with your Database.

Answer 3

You would first need to know the tables in which it's possible to have the entry. Use a loop to iterate over those tables and run the query, each time returning a result set and testing if records exist in the result set. This will tell you what tables have the entry.

General Approach:

$array = array("table1", "table2", "table3", "table4", "table5");
foreach($array as $table) {
    //build your query using the table name
    $query = "SELECT something FROM " .  $table;
    //exec your query against your db and return results
    //test if records exist in result set.  If true, you know the table name based on the loop iteration ($table).
}