I have a below table(#Temp):
RowNo Item
1 A
2 B
My requirement is if Item equals to B do action.
declare #count int = 1
WHILE(#count < (select count(*) from #Temp))
Begin
// Here I have to access my column name(Item) , so that I can check its value to B
set #count = #count + 1
End
Please suggest
You can use DESCRIBE:
DESCRIBE my_table;
Or in newer versions you can use INFORMATION_SCHEMA:
SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'my_database' AND TABLE_NAME = 'my_table';
Or you can use SHOW COLUMNS:
SHOW COLUMNS FROM my_table;
Related
There are too many tables in my SQL Server db. Most of them have an 'id' column, but some do not. I want to know which table(s) doesn't have the 'id' column and to count the rows where id=null if an 'id' column exists. The query results may look like this:
TABLE_NAME | HAS_ID | ID_NULL_COUNT | ID_NOT_NULL_COUNT
table1 | false | 0 | 0
table2 | true | 10 | 100
How do I write this query?
Building query:
WITH cte AS (
SELECT t.*, has_id = CASE WHEN COLUMN_NAME = 'ID' THEN 'true' ELSE 'false' END
FROM INFORMATION_SCHEMA.TABLES t
OUTER APPLY (SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS c
WHERE t.TABLE_NAME = c.TABLE_NAME
AND t.[TABLE_SCHEMA] = c.[TABLE_SCHEMA]
AND c.COLUMN_NAME = 'id') s
WHERE t.TABLE_SCHEMA IN (...)
)
SELECT
query_to_run = REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
'SELECT tab_name = ''<tab_name>'',
has_id = ''<has_id>'',
id_null_count = <id_null_count>,
id_not_null_count = <id_not_null_count>
FROM <schema_name>.<tab_name>'
,'<tab_name>', TABLE_NAME)
,'<schema_name>', TABLE_SCHEMA)
,'<has_id>', has_id)
,'<id_null_count>', CASE WHEN has_id = 'false' THEN '0' ELSE 'SUM(CASE WHEN id IS NULL THEN 1 END)' END)
,'<id_not_null_count>', CASE WHEN has_id = 'false' THEN '0' ELSE 'COUNT(id)' END)
FROM cte;
Copy the output and execute in separate window. UNION ALL could be added to get single resultset.
db<>fiddle demo
This might be useful for you... lists out the row count for all tables that have an "id" column. It filters out tables that start with "sys" because those are mostly internal tables. If you have a table that starts with "sys", you'll probably want to delete that part of the WHERE clause.
SELECT DISTINCT OBJECT_NAME(r.[object_id]) AS [TableName], [row_count] AS [RowCount]
FROM sys.dm_db_partition_stats r
WHERE index_id = 1
AND EXISTS (SELECT 1 FROM sys.columns c WHERE c.[object_id] = r.[object_id] AND c.[name] = N'id')
AND OBJECT_NAME(r.[object_id]) NOT LIKE 'sys%'
ORDER BY [TableName]
Note you can change the "c.[name] = N'id'" to be any column name, or even change the "=" to "<>" to find only tables without an id column
pmbAustin answers how to list all tables without "ID" column.
To know how many rows in each table, SQL Server has a built-in report for you.
Right click the database in SSMS, click "Reports", "Standard Reports" then "Disk Usage by Table"
You now know how many rows in each table, and from pmbAustin's answer you know how which tables do and do not have "ID" columns. with a simple Vlookup in Excel you can combine these two datasets to arrive at any answer you wish.
This will give you the info about which tables have or not have column named "ID":
SELECT Table_Name
, case when column_name not like '%ID%' then 'false'
else 'true'
end as HAS_ID
FROM INFORMATION_SCHEMA.COLUMNS;
Here is a small demo
And here is one way that you can use to select all the tables that have columns named ID and if this columns are null or not:
CREATE TABLE #AllIDSNullable (TABLE_NAME NVARCHAR(256) NOT NULL
, HAS_ID VARCHAR(10)
, ID_NULL_COUNT INT DEFAULT 0
, ID_NOT_NULL_COUNT INT DEFAULT 0);
DECLARE CT CURSOR FOR
SELECT Table_Name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE column_name = 'ID';
DECLARE #name NVARCHAR(MAX), #SQL NVARCHAR(MAX);
OPEN CT; FETCH NEXT FROM CT INTO #name;
WHILE ##FETCH_STATUS=0 BEGIN
SET #SQL = 'INSERT #AllIDSNullable (TABLE_NAME , HAS_ID) SELECT Table_Name, case when column_name not like ''%ID%'' then ''false'' else ''true'' end FROM INFORMATION_SCHEMA.COLUMNS;';
EXEC (#SQL);
SET #SQL = 'UPDATE #AllIDSNullable SET ID_NULL_COUNT = (SELECT COUNT(*) FROM ['+#name+'] WHERE ID IS NULL), ID_NOT_NULL_COUNT = (SELECT COUNT(*) FROM ['+#name+'] WHERE ID IS NOT NULL) WHERE TABLE_NAME='''+#name+''';';
EXEC (#SQL);
FETCH NEXT FROM CT INTO #name;
END;
CLOSE CT;
SELECT *
FROM #AllIDSNullable;
Here is a demo
Result:
I have a audit table that has about 8 million records. I have recently added two new column which I need to update from existing column with some rules/conditions. Basically initially, whenever a FK was updated in a table, it was storing old and new FK ids into the audit table. for example
Table A
ID Name
1 First A
2 Second A
3 Third A
Table B
ID AID Name
1 1 First B
2 1 Second B
3 2 Third B
Audit
ID TableName FieldName OldValue NewValue
now if i update first record of the table B
from 1 1 First B to 1 3 First B then the audit table will store the change as
Audit
ID TableName FieldName OldValue NewValue
1 Table B AID 1 3
Now I have updated Audit table to store actual Text value of the FK i.e above change will be stored as
Audit
ID TableName FieldName OldValue NewValue OldText NewText
1 Table B AID 1 3 First A Third A
The problem is I already have about 8 million records that I need to new columns for. I have written below query to do that
declare #sql nvarchar(max);
declare #start int = 1
while #start <= 8000000
begin
select top 10000 #sql = COALESCE(#sql+'Update Audit set ','Update Audit set') +
isnull(' OldText = ('+ dbo.GetFKText(i.TableName, i.FieldName)+case when len(isnull(i.OldValue,'')) < 1 then null else i.OldValue end +'),',' OldText = OldValue, ') +
isnull(' NewText = ('+ dbo.GetFKText(i.TableName, i.FieldName)+case when len(isnull(i.NewValue,'')) < 1 then null else i.NewValue end +')',' NewText = NewValue ') +
' where AuditID = '+cast(i.AuditID as nvarchar(200))+' and lower(ltrim(rtrim(TableName))) <> ''audit'';'
from Audit i where i.AuditID >= #start
exec sp_executesql #sql
set #start = #start+10000;
end
get text function (basically I getting column that has name = (TableName)+'Name' or (TablName)+(SomeText)+'Name' this just a convention that I have followed in all the tables)
declare #res nvarchar(max)='';
declare #fn nvarchar(200);
declare #ttn nvarchar(200);
declare #tcn nvarchar(200);
SELECT top 1
#ttn = kcu.table_name
,#tcn = kcu.column_name
FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE ccu
INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc
ON ccu.CONSTRAINT_NAME = rc.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu
ON kcu.CONSTRAINT_NAME = rc.UNIQUE_CONSTRAINT_NAME
Where ccu.TABLE_NAME = #TableName and ccu.COLUMN_NAME = #FieldName
if isnull(#ttn,'') != '' and ISNULL(#tcn,'') != ''
begin
select #fn= COLUMN_NAME
from (SELECT top 1 COLUMN_NAME ,
case when COLUMN_NAME like (#ttn+'Name') then 0
when COLUMN_NAME like (#ttn+'%Name') then 1
when COLUMN_NAME like (#ttn+'Code') then 2
when COLUMN_NAME like (#ttn+'%Code') then 3 else 4 end as CPriority
FROM JVO.INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = #ttn and (COLUMN_NAME like '%Name' or COLUMN_NAME like '%Code'
)
order by CPriority) as aa;
RETURN 'select '+#fn+' from '+#ttn+' where '+#tcn+' = ';
end
return null;
Its working but really slow, it update about 1 million records in 13 hours. can anyone help to improve this query or suggest alternative way to update it.
Thanks
I created a temp table #test containing 3 fields: ColumnName, TableName, and Id.
I would like to see which rows in the #test table (columns in their respective tables) are not empty? I.e., for every column name that i have in the ColumnName field, and for the corresponding table found in the TableName field, i would like to see whether the column is empty or not. Tried some things (see below) but didn't get anywhere. Help, please.
declare #LoopCounter INT = 1, #maxloopcounter int, #test varchar(100),
#test2 varchar(100), #check int
set #maxloopcounter = (select count(TableName) from #test)
while #LoopCounter <= #maxloopcounter
begin
DECLARE #PropIDs TABLE (tablename varchar(max), id int )
Insert into #PropIDs (tablename, id)
SELECT [tableName], id FROM #test
where id = #LoopCounter
set #test2 = (select columnname from #test where id = #LoopCounter)
declare #sss varchar(max)
set #sss = (select tablename from #PropIDs where id = #LoopCounter)
set #check = (select count(#test2)
from (select tablename
from #PropIDs
where id = #LoopCounter) A
)
print #test2
print #sss
print #check
set #LoopCounter = #LoopCounter + 1
end
In order to use variables as column names and table names in your #Check= query, you will need to use Dynamic SQL.
There is most likely a better way to do this but I cant think of one off hand. Here is what I would do.
Use the select and declare a cursor rather than a while loop as you have it. That way you dont have to count on sequential id's. The cursor would fetch fields columnname, id and tablename
In the loop build a dynamic sql statement
Set #Sql = 'Select Count(*) Cnt Into #Temp2 From ' + TableName + ' Where ' + #columnname + ' Is not null And ' + #columnname <> '''''
Exec(#Sql)
Then check #Temp2 for a value greater than 0 and if this is what you desire you can use the #id that was fetched to update your #Temp table. Putting the result into a scalar variable rather than a temp table would be preferred but cant remember the best way to do that and using a temp table allows you to use an update join so it would well in my opinion.
https://www.mssqltips.com/sqlservertip/1599/sql-server-cursor-example/
http://www.sommarskog.se/dynamic_sql.html
Found a way to extract all non-empty tables from the schema, then just joined with the initial temp table that I had created.
select A.tablename, B.[row_count]
from (select * from #test) A
left join
(SELECT r.table_name, r.row_count, r.[object_id]
FROM sys.tables t
INNER JOIN (
SELECT OBJECT_NAME(s.[object_id]) table_name, SUM(s.row_count) row_count, s.[object_id]
FROM sys.dm_db_partition_stats s
WHERE s.index_id in (0,1)
GROUP BY s.[object_id]
) r on t.[object_id] = r.[object_id]
WHERE r.row_count > 0 ) B
on A.[TableName] = B.[table_name]
WHERE ROW_COUNT > 0
order by b.row_count desc
How about this one - bitmask computed column checks for NULLability. Value in the bitmask tells you if a column is NULL or not. Counting base 2.
CREATE TABLE FindNullComputedMask
(ID int
,val int
,valstr varchar(3)
,NotEmpty as
CASE WHEN ID IS NULL THEN 0 ELSE 1 END
|
CASE WHEN val IS NULL THEN 0 ELSE 2 END
|
CASE WHEN valstr IS NULL THEN 0 ELSE 4 END
)
INSERT FindNullComputedMask
SELECT 1,1,NULL
INSERT FindNullComputedMask
SELECT NULL,2,NULL
INSERT FindNullComputedMask
SELECT 2,NULL, NULL
INSERT FindNullComputedMask
SELECT 3,3,3
SELECT *
FROM FindNullComputedMask
I have a table containing column names from another table. I want to run an update statement to update some values from that table, based off of the other.
EX:
TableA
ID|Column1|Column2
1 | 1.3 | 2.3
2 | 0 | 7
3 | 2.5 | 12.1
TableB
ID|ColumnName|MaxValue
1 | Column1 | NULL
2 | Column2 | NULL
Something along the lines of this:
So in this case, I would want to update MaxValue in TableB to be the max value from TableA where ColumnName is a colum in TableA.
Is this possible?
You can do it with a cursor and some dynamic sql. This isn't the best thing to do but if you needed a quick and dirty solution here you go:
DECLARE #colName VARCHAR(50), #str VARCHAR(2000), #id int
DECLARE c CURSOR FOR
SELECT id, columnName
FROM tableB
OPEN c
FETCH NEXT FROM c INTO #id, #columnName
WHILE ##fetch_status = 0
BEGIN
SET #str = 'update tableB set MaxValue = ( select max(' + #colName + ') from
tableA ) where id = ' + CONVERT(VARCHAR, #id)
EXEC ( #str )
FETCH NEXT FROM c INTO #id, #columnName
END
CLOSE c
DEALLOCATE c
If you do not want to use dynamic SQL, you could always do something like this
Update TableB
Set MaxValue = MaxValues.MaxValue
From TableB
Join
(
Select MaxValue = Max(Column1)
,ColumnName = 'Column1'
From TableA
Union All
Select MaxValue = Max(Column2)
,ColumnName = 'Column2'
From TableA
-- Union All ... and so on for all columns
) MaxValues
On TableB.ColumnName = MaxValues.ColumnName
Remember, if the TableA DDL changes, you must update this DML.
I have a select statement which I want to convert into an update statement for all the columns in the table which have the name Variable[N].
For example, I want to do these things:
I want to be able to convert the SQL below into an update statement.
I have n columns with the name variable[N]. The example below only updates column variable63, but I want to dynamically run the update on all columns with names variable1 through variableN without knowing how many variable[N] columns I have in advance. Also, in the example below I get the updated result into NewCol. I actually want to update the respective variable column with the results if possible, variable63 in my example below.
I want to have a wrapper that loops over column variable1 through variableN and perform the same respective update operation on all those columns:
SELECT
projectid
,documentid
,revisionno
,configurationid
,variable63
,ISNULL(Variable63,
(SELECT TOP 1
variable63
FROM table1
WHERE
documentid = t.documentid
and projectid=t.projectid
and configurationid=t.configurationid
and cast(revisionno as int) < cast(t.revisionno as int)
AND Variable63 is NOT NULL
ORDER BY
projectid desc
,documentid desc
,revisionno desc
,configurationid desc
)) as NewCol
FROM table1 t;
There's no general way to loop through variables in SQL, you're supposed to know exactly what you want to modify. In some databases, it will be possible to query system tables to dynamically build an update statement (I know how to do that in InterBase and it's decessor Firebird), but you haven't told us anything which database engine you're using.
Below is a way you could update several fields that are null, COALESCE and CASE are two way of doing the same thing, as is using LEFT JOIN or NOT EXISTS. Use the ones you and your database engine is most comfortable with. Beware that all records will be updated, so this is not a good solution if your database contains millions of records, each record is large and you want this query to be executed lots of times.
UPDATE table1 t
SET t.VARIABLE63 =
COALESCE(t.VARIABLE63,
(SELECT VARIABLE63
FROM table1 t0
LEFT JOIN table1 tNot
ON tNot.documentid = t.documentid
AND tNot.projectid=t.projectid
AND tNot.configurationid=t.configurationid
AND cast(tNot.revisionno as int) > cast(t0.revisionno as int)
AND cast(tNot.revisionno as int) < cast(t.revisionno as int)
AND tNot.Variable63 is NOT NULL
WHERE t0.documentid = t.documentid
AND t0.projectid=t.projectid
AND t0.configurationid=t.configurationid
AND cast(t0.revisionno as int) < cast(t.revisionno as int)
AND t0.Variable63 is NOT NULL
AND tNot.Variable63 is NULL)),
t.VARIABLE64 = CASE WHEN t.VARIABLE64 IS NOT NULL then t.VARIABLE64
ELSE (SELECT VARIABLE64
FROM table1 t0
WHERE t0.documentid = t.documentid
AND t0.projectid=t.projectid
AND t0.configurationid=t.configurationid
AND cast(t0.revisionno as int) < cast(t.revisionno as int)
AND t0.Variable64 is NOT NULL
AND NOT EXISTS(SELECT 1
FROM table1 tNot
WHERE tNot.documentid = t.documentid
AND tNot.projectid=t.projectid
AND tNot.configurationid=t.configurationid
AND cast(tNot.revisionno as int) > cast(t0.revisionno as int)
AND cast(tNot.revisionno as int) < cast(t.revisionno as int)
AND tNot.Variable64 is NOT NULL)) END
OK I think I got it. Function that loops through columns and runs an update command per column.
DECLARE #sql NVARCHAR(1000),
#cn NVARCHAR(1000)--,
--#r NVARCHAR(1000),
--#start INT
DECLARE col_names CURSOR FOR
SELECT column_name
FROM information_schema.columns
WHERE table_name = 'PIVOT_TABLE'
ORDER BY ordinal_position
--SET #start = 0
DECLARE #op VARCHAR(max)
SET #op=''
OPEN col_names FETCH next FROM col_names INTO #cn
WHILE ##FETCH_STATUS = 0
BEGIN
--print #cn
IF UPPER(#cn)<> 'DOCUMENTID' and UPPER(#cn)<> 'CONFIGURATIONID' and UPPER(#cn)<> 'PROJECTID' and UPPER(#cn)<> 'REVISIONNO'
BEGIN
SET #sql = 'UPdate pt
set pt.' + #cn + ' = ((SELECT TOP 1 t.' + #cn + ' FROM pivot_table t WHERE t.documentid = pt.documentid and t.projectid=pt.projectid
and t.configurationid=pt.configurationid and cast(t.revisionno as int) < cast(pt.revisionno as int) AND t.' + #cn + ' is NOT NULL
ORDER BY revisionno desc)) from PIVOT_TABLE pt where pt.' + #cn + ' is NULL;'
EXEC Sp_executesql
#sql
--print #cn
END
FETCH next FROM col_names INTO #cn
END
CLOSE col_names
DEALLOCATE col_names;