We often use join clauses to query rows in a table that have (in the case of INNER JOIN) or may not have (in the case of LEFT JOIN) corresponding rows in another table.The SQL Server (Transact-SQL) UPDATE statement is used to update existing records in a table in a SQL Server database.There are 3 syntaxes for the UPDATE statement depending on whether you are performing a traditional update or updating one table with data from another table.
In recent times I have seen a developer writing a cursor to update a table. We want to update the value from Table2 to Table1 for the rows where Col1 is 21 and 31.
When asked the reason was he had no idea how to use multiple tables with the help of the JOIN clause in the UPDATE statement. Additionally, we want to update the values of Col2 and Col3 only.
When you look at this it looks very simple but when we try to think the solution, I have seen developers coming up with many different solutions for example sometime they write cursor, table variables, local variables etc.
However, the easiest and the most clean way is to use JOIN clause in the UPDATE statement and use multiple tables in the UPDATE statement and do the task. UPDATE Table SET Col1 = REPLACE(Col1, ‘.’, ‘ ‘) – If migrating data from one table (or database) to another I will use insert with select, this can allow for data manipulation also. CID IN (1002)here i am Getting an Error Error: The multi-part identifier “t1. Help me in this soon as possible My mail ID [email removed]REGARDSASIMI have an issue with how SQL behaves when doing these updates in the following scenarios. I created a new request using all of your example statements. My question is where do the are the apparent alias names of t1 and t2 come frome?
As you can see that using JOIN clause in UPDATE statement it makes it very easy to update data in one table from another table. I will often use the SSMS Script As options to get the insert statement and then write the select to return the correct values to be inserted. Amount=’123654′ FROM Customer t1 INNER JOIN Payment t2 ON t1. Lets say one day someone comes along and adds 1 row to Table 2 like this: Col1 Col2 Col3 21 33 Three-Three SQL server will randomly pick one of the rows where Col1=21 from table 2 and update to table 1 for you. Bad thing is that no one will know about it until a business user calls you and asks why they get a diff value everyday. In the querysql window, If I hover over the “t2” in the line SET Col2 = t2.
You can additionally use MERGE statement to do the same as well, however I personally prefer this method. This works for existing tables, whilst Select Into does not. But you should at least mention the ‘new’ merge statement, here’s a good link for you: ; DNice post, Pinal, as always. Col1 IN (21, 31)Reason: Some time Table1 joined to itself by some criteria and “update t1” resolves ambiguous names Hi Folks My Question: I need to update different columns in different table. I have specific character that needs to be replaced with ”In each table I have to update a specific column. Approach: I thought of creating arrays for tab n col Check the code below n help me with this CREATE Or REPLACE TYPE TABARRAY AS VARRAY(3) OF VARCHAR2(10); CREATE Or REPLACE TYPE COLARRAY AS VARRAY(3) OF VARCHAR2(10); CREATE Or REPLACE TYPE ILLARRAY AS VARRAY(3) OF VARCHAR2(10); DECLARE type TABARRAY IS VARRAY(5) OF VARCHAR2(10); TABNAMES TABARRAY; type COLARRAY IS VARRAY(5) OF VARCHAR2(10); COLNAMES COLARRAY; type ILLARRAY IS VARRAY(5) OF VARCHAR2(10); ILLNAMES ILLARRAY; TOTAL INTEGER; BEGIN TABNAMES :=TABARRAY(‘siebel. S_SRV_REQ’); COLNAMES :=COLARRAY(‘X_SPECIAL_SERVICE_CD’,’X_SGSTNS_PREV’); ILLNAMES :=ILLARRAY(‘HE’,’EA’); TOTAL :=TABNAMES. COUNT; FOR I IN TOTAL LOOP FOR J IN ILLTOTAL LOOP UPDATE TABNAMES(I) SET COLNAMES(I)=REPLACE(COLNAMES(I), ILLNAMES(J),”); END LOOP; END LOOP; END; How can i update different Table Column ???? Col2, the server code knows this is “fullyqualifiedpath”Table2 AS t2 and similar for “t1” Is this really an alias or is it something else and how are the name t1 and t2 derived? I was change the statement like below, and got the same result, my question is how different in these two statements ?
Let us clean up the clause by dropping the tables which we have created. For rookies, of course :) I recommend to everybody to read Izik Ben-Gan’s “T-SQL Fundamentals” to know such a basic stuff like JOINs in DML, MERGE, table expressions, subqueries, isolation lvls and blocking, and algebra fundamentals of SQL-language.
This will save Pinal’s time for real )))I only wonder, why you’re not using INSERT VALUES instead of INSERT SELECT UNION ALL – you can really make use of this tiny liitle feature called “Table Value Constructor” and define virtual table expressions on the basis if VALUES.
Anyway, SELECT UNION ALL still works out for anything below SQL Server 2008. Just little note…I prefer to use table name “t1” instead “Table1” in “UPDATE” statement: UPDATE t1 — instead Table1 SET Col2 = t2.
I was change the statement like below, and got the same result, my question is what’s different in these two statements ?
Col1 IN (21, 31) GOperformance wise I liked; (not my! guess you already covered it somewhere..; WITH CTE AS (SELECT T1.