SQL Query to search records in multiple tables - sql

Question

I'm trying to implement a search feature. I need to look into multiple tables in SQL database using a text-string. Currently, I'm only looking into 3 tables i.e.,
Table Items:
[dbo].[Items]
(
[ItemID] INT IDENTITY (1, 1) NOT NULL,
[CategoryID] INT NOT NULL,
[BrandID] INT NOT NULL,
[ItemName] NVARCHAR(MAX) NOT NULL,
[ItemPrice] DECIMAL(18, 2) NOT NULL,
[imageUrl] NVARCHAR(MAX) NULL,
CONSTRAINT [PK_dbo.Items]
PRIMARY KEY CLUSTERED ([ItemID] ASC),
CONSTRAINT [FK_dbo.Items_dbo.Brands_BrandID]
FOREIGN KEY ([BrandID]) REFERENCES [dbo].[Brands] ([BrandID]),
CONSTRAINT [FK_dbo.Items_dbo.Categories_CategoryID]
FOREIGN KEY ([CategoryID]) REFERENCES [dbo].[Categories] ([CategoryID])
)
Table Categories:
[dbo].[Categories]
(
[CategoryID] INT IDENTITY (1, 1) NOT NULL,
[Name] NVARCHAR (MAX) NULL,
CONSTRAINT [PK_dbo.Categories]
PRIMARY KEY CLUSTERED ([CategoryID] ASC)
)
Table Brands:
[dbo].[Brands]
(
[BrandID] INT IDENTITY (1, 1) NOT NULL,
[Name] NVARCHAR (MAX) NULL,
CONSTRAINT [PK_dbo.Brands]
PRIMARY KEY CLUSTERED ([BrandID] ASC)
)
Any records that may contain the supplied text-string must be fetched out. I'm a newbie on SQL knowledge. This is my implementation is:
SELECT *
FROM Items
WHERE ItemName LIKE 'cocacola'
SELECT *
FROM Categories
WHERE Name LIKE 'cocacola'
SELECT *
FROM Brands
WHERE Name LIKE 'cocacola'
which is obviously incorrect. Can someone please guide.
Thanks.

Answer 1

If you want to return a substring search, it might be slow depending on how much data you have.
If you are able to pre-specify the tables, and want a single search that searches all and returns matches across all tables, you will want something like this:
SELECT
'Items' as table_name,
item_id as record_id,
ItemName AS found
FROM
Items
WHERE
ItemName LIKE '%cocacola%'
UNION
SELECT
'Categories' as table_name,
CategoryID AS record_id,
Name AS found
FROM
Categories
WHERE
Name LIKE '%cocacola%'
UNION
SELECT
'Brands' as table_name,
BrandID AS record_id,
Name AS found
FROM
Brands
WHERE
Name LIKE '%cocacola%'
The UNION will append the results from one query to another.
It will be slow if you have a lot of data

Answer 2

You solution is not incorrect. You run three queries. Each against a different Table. Depending on your use case this is probably fine.
You can join the tables if you want to search all tables with only one query. This is probably slower than running three queries because the database has to match the values together.
SELECT *
FROM Items
FULL OUTER JOIN Categories ON Categories.CategoryID = Items.CategoryID
FULL OUTER JOIN Brands ON Brands.BrandID = Items.BrandID
WHERE Items.ItemName LIKE 'cocacola'
AND Categories.Name LIKE 'cocacola'
AND Brands.Name LIKE 'cocacola'
If you get a hit in the category name with this query, the category will be listed for every item that's associated with this category.

Answer 3

It sounds like you might want to try using a union to join together the results of all three queries.
For example:
SELECT ItemID, ItemName
FROM Items
WHERE ItemName = 'cocacola'
UNION
SELECT CategoryID, Name
FROM Categories
WHERE Name = 'cocacola'
UNION
SELECT BrandID, Name
FROM Brands
WHERE Name = 'cocacola'
One note about union is that you have to make sure that each part of the query is returning the same number of columns with the same datatype in the same order.