I'm trying to learn SQL queries, and I've encountered things like this:
SELECT name FROM customer_list t
WHERE ...
What does the t mean? Is it like the name of an instance of that table?
Thanks!
The t is an alias that you can refer to instead of the table name in your query. If you have only one table you're querying from it isn't very useful, but it comes in hand when you have multiple tables (e.g., in join clauses and you want to avoid writing the entire long table name whenever you refer to it. E.g.:
SELECT t.name
FROM some_long_table_name t
JOIN some_other_long_table_name s ON t.id = s.id
Related
I'm trying to Replace the schema in existing table using BQ. There are certain fields in BQ which have 3-5 level schema dependency.
For Ex. comsalesorders.comSalesOrdersInfo.storetransactionid this field is nested under two fields.
Since I'm using this to replace existing table, I can not change the field names in query.
The query looks similar to this
SELECT * REPLACE(comsalesorders.comSalesOrdersInfo.storetransactionid AS STRING) FROM CentralizedOrders_streaming.orderStatusUpdated, UNNEST(comsalesorders) AS comsalesorders, UNNEST(comsalesorders.comSalesOrdersInfo) AS comsalesorders.comSalesOrdersInfo
BQ enables unnesting first schema field but presents problem for 2nd nesting.
What changes do I need to make to this query to use UNNEST() for such depedndent schemas ?
Given that you don't have a schema, I will try to provide a generalized answer. Please try to understand the difference between the 2 queries.
-- Provide an alias for each unnest (as if each is a separate table)
select c.stuff
from table
left join unnest(table.first_level_nested) a
left join unnest(a.second_level_nested) b
left join unnest(b.third_level_nested) c
-- b and c won't work here because you are 'double unnesting'
select c.stuff
from table
left join unnest(table.first_level_nested) a
left join unnest(first_level_nested.second_level_nested) b
left join unnest(first_level_nested.second_level_nested.third_level_nested) c
I'm not sure I understand your question, but as I could guess, you want to change one column type to another type, such as STRING.
The UNNEST function is only used with columns that are array types, for example:
"comsalesorders":["comSalesOrdersInfo":{}, comSalesOrdersInfo:{}, comSalesOrdersInfo:{}]
But not with this kind of columns:
"comSalesOrdersInfo":{"storeTransactionID":"X1056-943462","ItemsWarrenty":0,"currencyCountry":"USD"}
Therefore, if a didn't misunderstand your question, I would make a query like this:
SELECT *, CAST(A.comSalesOrdersInfo.storeTransactionID as STRING)
FROM `TABLE`, UNNEST(comsalesorders) as A
I am completely lost thinking about how do I solve this challenge of data retrieving.
I have this two tables: MY_DATA and MY_DATA_CHANGE in my Oracle database.
I wanted to select data some thing like this:
SELECT ALL COLUMNS
FROM MY_DATA
WHERE ID IN (1,2,4,5) FROM MY_DATA
BUT IF ANY ID IS PRESENT IN (1,2,4,5) IN MY_DATA_CHANGE
THEN USE ROW FROM MY_DATA_CHANGE
So my overall result must look like:
I can only use SQL not stored procedure, as this query is going to be part of another very big query (legacy code written long back) (will be used in Crystal reports tool to create report).
So guys please help. My column data contains CLOB and the usual UNION logic does not work on them.
How do I do it ?
SELECT
m.Id
,COALESCE(c.CLOB1,m.CLOB1) as CLOB1
,COALESCE(c.CLOB2,m.CLOB2) as CLOB2
FROM
MY_DATA m
LEFT JOIN MY_DATA_CHANGE c
ON m.Id = c.Id
WHERE
m.ID IN (1,2,4,5)
The way I would choose to do that is via a LEFT JOIN between the two tables and then use COALESCE().
I am trying to join two views I created, however I am joining them using their common field (cAuditNumber).
The issue is, once I have done the joins, it will not let me create the view as it cannot have the field name cAuditNumber twice.
Is the cAuditNumber the PK I should use?
How do I correct this and still join the tables?
CREATE VIEW KFF_Sales_Data_Updated AS
SELECT CustSalesUpdated.*, StkSalesUpdated.*
FROM CustSalesUpdated
INNER JOIN StkSalesUpdated
ON StkSalesUpdated.cAuditNumber = CustSalesUpdated.cAuditNumber
I get the following error:
Msg 4506, Level 16, State 1, Procedure KFF_Sales_Data_Updated, Line 2
Column names in each view or function must be unique. Column name 'cAuditNumber' in view or function 'KFF_Sales_Data_Updated' is specified more than once.
Substitute your own column names instead of ColumnA, Column B, etc, but it should follow this format:
CREATE VIEW KFF_Sales_Data_Updated AS
SELECT CustSalesUpdated.cAuditNumber
,CustSalesUpdated.ColumnA
,CustSalesUpdated.ColumnB
,CustSalesUpdated.ColumnC
,StkSalesUpdated.ColumnA as StkColumnA
,StkSalesUpdated.ColumnB as StkColumnB
,StkSalesUpdated.ColumnC as StkColumnC
FROM CustSalesUpdated
INNER JOIN StkSalesUpdated
ON StkSalesUpdated.cAuditNumber = CustSalesUpdated.cAuditNumber
You only have to alias duplicate columns using "as", or you can use it to rename any column that you so desire.
CREATE VIEW KFF_Sales_Data_Updated AS
SELECT csu.cAuditNumber cAuditNumber1 , ssu.cAuditNumber cAuditNumber2
FROM CustSalesUpdated csu
INNER JOIN StkSalesUpdated ssu
ON StkSalesUpdated.cAuditNumber = CustSalesUpdated.cAuditNumber
You could add any other column in the select statement from the two tables but if there are two column with the same name you should give them aliases
Using select * is a bad practice in general. On the other hand, it is a good practice to alias your table names and columns. Especially in your case, your table names as well as your same columns name(across two tables) could use aliases. The database is confused as to which cAuditNumber is coming from where. So, alias comes in handy.
CREATE VIEW KFF_Sales_Data_Updated
AS
SELECT
csu.cAuditNumber
,csu.Col1
,csu.Col2
,csu.Col3
,ssu.Col1 AS StkCol1
,ssu.Col2 AS StkCol2
,ssu.Col3 AS StkCol3
FROM CustSalesUpdated csu
INNER JOIN StkSalesUpdated ssu ON csu.cAuditNumber = ssu.cAuditNumber
When I used this query above exception has thrown
SELECT FINQDET.InquiryNo,FINQDET.Stockcode,FINQDET.BomQty,FINQDET.Quantity,FINQDET.Rate,FINQDET.Required,FINQDET.DeliverTo,FSTCODE.TitleA AS FSTCODE_TitleA ,FSTCODE.TitleB AS FSTCODE_TitleB,FSTCODE.Size AS FSTCODE_Size,FSTCODE.Unit AS FSTCODE_Unit, FINQSUM.TITLE AS FINQSUM_TITLE,FINQSUM.DATED AS FINQSUM_DATED
FROM FINQSUM , FINQDET left outer join [Config]..FSTCODE ON FINQDET.Stockcode=FSTCODE.Stockcode
WHERE FINQDET.InquiryNo=FINQSUM.INQUIRYNO
ORDER BY FINQDET.Stockcode,FINQDET.InquiryNo
but if I used below query problem solved,
SELECT FINQDET.InquiryNo,FINQDET.Stockcode,FINQDET.BomQty,FINQDET.Quantity,FINQDET.Rate,FINQDET.Required,FINQDET.DeliverTo,FSTCODE.TitleA AS FSTCODE_TitleA ,FSTCODE.TitleB AS FSTCODE_TitleB,FSTCODE.Size AS FSTCODE_Size,FSTCODE.Unit AS FSTCODE_Unit,
FINQSUM.TITLE AS FINQSUM_TITLE,FINQSUM.DATED AS FINQSUM_DATED
FROM FINQSUM As FINQSUM , FINQDET As FINQDET left outer join [Config]..FSTCODE As FSTCODE ON FINQDET.Stockcode=FSTCODE.Stockcode
HERE FINQDET.InquiryNo=FINQSUM.INQUIRYNO
ORDER BY FINQDET.Stockcode,FINQDET.InquiryNo
Please can you explain Why using Alias better than using actual table names
The table [Config]..FSTCODE is qualified with database name which works fine if you use alias. Otherwise you need to qualify full name as it is from different database
Looks like FSTCODE is a table in a different DB. In the first query, though the JOIN uses the DB name to identify the table, the ON statement does not. The second statement adresses this by using an ALIAS
You can also modify the first statement as
left outer join [Config]..FSTCODE
ON FINQDET.Stockcode=[Config]..FSTCODE.Stockcode
An alias allows you to reference a set without using the fullname. It saves you typing and allows you to express contextual information to the reader.
Hi i got a little problem right now i'm doing Stored Proc in sql server. I wanna get some result from multiple table and put it into a temporary table. So I thought i could use a "Select into" statement wich work fine until i decided to add multiple select into the temporary table. For example: Here's my code:
while #Compteur <= #wrhCodeEnd
select lp.lotQty ,lp.lotID into ZeTable from TB_lotLot ltlt
inner join TB_lotPal lp on ltlt.lotID=lp.lotID
inner join TB_palSuper ps ON lp.spID=ps.spID
inner join TB_expExpeditionLot eel ON eel.lotID=lp.spID
where ps.wrhID <> #Compteur and
ltlt.wrhID = #Compteur and
lp.lotID not in(select ZeTable.lotID from ZeTable)
the thing is I don't know if I can make multiple select into on the same temporary table and I also wanna check with a where clause the information in the table is not already there.
Thx in Advance
You can create temporary table and can use insert statement to add records with required columns and can drop it after use.