MySql - Create view to read from Multiple Tables

Question

I have archived some old line items for invoices that are no longer current but still need to reference them. I think I need to create a VIEW but not really understanding it. Ca

Answer 1

You can use UNION :

SELECT a.* FROM a 
  UNION
SELECT b.* FROM b;

You just need to have the same number and type of column in your different queries. As far as I remember, you can add test in sub-queries, but I'm not sure you can order on the global result.

http://dev.mysql.com/doc/refman/4.1/en/union.html

Answer 2

You can use the MERGE Storage Engine to create a virtual table that's the union of two real tables:

CREATE TABLE Invoice_LineItem_All 
(
  `LineItem_ID` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,
  `LineItem_ChargeType` VARCHAR(64) NOT NULL DEFAULT '',
  `LineItem_InvoiceID` INT(11) UNSIGNED DEFAULT NULL,
  `LineItem_Amount` DECIMAL(11,4) DEFAULT NULL,
  `LastUpdatedAt` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  KEY (`LineItem_ID`),
  KEY `LastUpdatedAt` (`LastUpdatedAt`),
  KEY `LineItem_InvoiceID` (`LineItem_InvoiceID`)
) ENGINE=MERGE UNION=(Invoice_LineItem_Archived, Invoice_LineItem);