I have an update query which i thought should update multiple rows in one request..
UPDATE myTable SET val = val + 1 WHERE id = "X" or "Y"
however this only seems to update X's val not Y's as well
UPDATE myTable
SET val = val + 1
WHERE id = 'X'
OR id = 'Y'
or
WHERE id in ('X', 'Y')
Your query works fine, but will ignore "Y" values because it will be evaluated as:
UPDATE myTable SET val = val + 1 WHERE id = "X" or FALSE
because "Y" will be evaluated as 0 which is false.
You have to fix your where condition to
(id = "X" or id = "Y")
Related
I would like to do the following.
Update a field based on the value of another field like
update table set if(fielda=1){fieldb=2 fieldc=3}else{fieldd=2 fielde=3}
I know this is not valid mysql but its the best way for me to describe the problem.
update table set
b = case when a = 1 then 2 else b end,
c = case when a = 1 then 3 else c end,
d = case when a = 1 then d else 2 end,
e = case when a = 1 then e else 3 end
edit
according to your comment try this:
update table set
datefield_a = case when field_a = 1 then now() else datefield_a end,
datefield_b = case when field_a <> 1 then now() else datefield_b end
I think this syntax will achieve the result you attempted to specify.
UPDATE mytable
SET fieldb = CASE WHEN fielda = 1 THEN 2 ELSE fieldb END
, fieldc = CASE WHEN fielda = 1 THEN 3 ELSE fieldc END
, fieldd = CASE WHEN fielda = 1 THEN fieldd ELSE 2 END
, fielde = CASE WHEN fielda = 1 THEN fielde ELSE 3 END
The "trick" here is that we are updating all four columns, but in some "cases", we are assigning the current value of the column back to the column, resulting in no real change to the column value. (Once you get your mind bent around that idea, it's pretty easy.)
With MySQL, we do have a handy IF function (not available in most other RDBMS) that we can use to abbreviate that a bit, and achieve the same thing:
UPDATE mytable
SET fieldb = IF(fielda = 1, 2, fieldb)
, fieldc = IF(fielda = 1, 3, fieldc)
, fieldd = IF(fielda = 1, fieldd, 2)
, fielde = IF(fielda = 1, fielde, 3)
The pain is that you still have to repeat that same conditional test multiple times.
A single scan through the table (like these statements do), and getting all those assignments done in one fell swoop is going to be faster (and more efficient) than breaking this up and doing the assignments piecemeal using multiple statements.
Update myTable SET field = 1 (if field = 0 or if field is null) where myid = 12345;
Update myTable SET field = 0 (if field = 1) where myid = 12345;
What is the best way to transform this Pseudocode in proper SQL for Oracle and MySQL?
You could simply use the modulo like this:
UPDATE myTable SET field = (field + 1) % 2 WHERE myId = 12345;
Due to the lack of a real boolean in both DBMS you need a case statement:
update myTable
set the_column = case when the_column = 1 then 0 else 1 end
where myId = 12345;
This assumes that the column never has different values than 0 and 1
I have a database table and What I required to do is that,
I need to update the column with the column name 'Co15' of every rows according to the following conditions
Co15 = SAMPLE if Co13 = 'c1' AND Col2 = 'b4'
Co15 = LIST if Co13 = 'c6'
Currently I am running each update query separately as follows
UPDATE tblname SET Co15 = 'SAMPLE' WHERE Co13 = 'c1' AND Col2 = 'b4';
UPDATE tblname SET Co15 = 'LIST' WHERE Co13 = 'c6';
But wanted to know if there is any way where I could run only one update query all at once.
Thanks
Try this
UPDATE tblname SET Co15=
CASE
WHEN Co13 = 'c1' AND Col2='b4' THEN 'SAMPLE'
WHEN Co13 = 'c6' THEN 'LIST'
END
exactly getting the output to as following as:
UPDATE tblname
SET col5= CASE
WHEN col3 = 'c1' AND col2 = 'b4' THEN 'SAMPL'
WHEN col3 = 'c6' THEN 'LIST'
END
example: sqlfiddle to click here
I have a flag in my database called published, I set this to 1 for a published row. My question is , is there a way to set all other rows to 0 and set a particular row to 1 with just one query.
At the moment im using:
$db->query("UPDATE my_table SET published = '0'");
$db->query("UPDATE my_table SET published = '1' WHERE id = '$id'");
UPDATE my_table SET published = IF (id = $id,1,0);
Use a CASE Statement
UPDATE my_table
SET published = CASE
WHEN id = '$id' THEN 1
ELSE 0 END
In MySQL, there's no boolean type (conditions return an integer), so this works too :
UPDATE my_table
SET published = (id = $id);
id = $id returns 0 if $id is different than id, else 1.
I have an update statement that updates fields x, y and z where id = xx.
In the table I have a few different x_created_datetime fields (for different portions of the record that are maintained/entered by different folks). I'd like to write a single query that will update this field if is null, but leave it alone if is not null.
So what I have is:
UPDATE newspapers
SET scan_notes = "data",
scan_entered_by = "some_name",
scan_modified_date = "current_unix_timestamp"
WHERE id = X
What I need is a way to add in the following, but still always update the above:
scan_created_date = "current_unix_timestamp"
where scan_created_date is null
I'm hoping I can do this without a second transaction to the DB. Any ideas on how to accomplish this?
Do this:
UPDATE newspapers
SET scan_notes = "data",
scan_entered_by = "some_name",
scan_modified_date = "current_unix_timestamp",
scan_created_date = COALESCE(scan_created_date, "current_unix_timestamp")
WHERE id = X
The COALESCE function picks the first non-null value. In this case, it will update the datestamp scan_created_date to be the same value if it exists, else it will take whatever you replace "current_unix_timestamp" with.
mySQL has an IFNULL function, so you could do:
UPDATE newspapers
SET scan_notes = "data",
scan_entered_by = "some_name",
scan_modified_date = "current_unix_timestamp"
scan_created_date = IFNULL( scan_created_date, "current_unix_timestamp" )
WHERE id = X
I think that what you're looking for is IF()
UPDATE newspapers
SET scan_notes = "data",
scan_entered_by = "some_name",
scan_modified_date = "current_unix_timestamp",
scan_created_date = IF(scan_created_date IS NOT NULL, "current_unix_timestamp", NULL)
WHERE id = X
You could use COALESCE() wich returns the first NON-NULL value):
scan_created_date = COALESCE(scan_created_date, "current_unix_timestamp")
You can do something like this:
UPDATE newspapers a, newspapers b
SET a.scan_notes = "data",
a.scan_entered_by = "some_name",
a.scan_modified_date = "current_unix_timestamp",
b.scan_created_date = "current_unix_timestamp"
WHERE a.id = X AND b.id = X AND b.scan_created_date is not NULL
Its like equivalent to Oracle's NVL.
You can use it like below in a prepared statement using parameters
UPDATE
tbl_cccustomerinfo
SET
customerAddress = COALESCE(?,customerAddress),
customerName = COALESCE(?,customerName),
description = COALESCE(?,description)
WHERE
contactNumber=?