I want to write a SELECT statement to show the list of fields in the table.
COLUMN
column_1
column_2
column_3
You can use the information schema tables, particularly columns:
select column_name
from INFORMATION_SCHEMA.COLUMNS
where table_schema = #schema_name and table_name = #table_name;
Note that this metadata is stored per database. So if you want a table in another database, you need three part naming:
select column_name
from <database>.INFORMATION_SCHEMA.COLUMNS
where table_schema = #schema_name and table_name = #table_name;
Yet one more option: This will return results on any table,ad-hoc query or even a stored procedure.
(using spt_values as a demonstration)
Example
Select column_ordinal
,name
,system_type_name
From sys.dm_exec_describe_first_result_set('Select * From master..spt_values',null,null )
Returns
In SQL Server you can also highlight the tablename in a query then press ALT+F1 to show the highlighted table info.
Related
I have table which has basically 2 rows containing the name of failure and the main table i want to write a query such that
Select main
from xyz
will return the table name like abc.
Now I want to get the data from the abc table
Select *
from
(select main
from xyz)
which returns abc.
How can I write it ?
You must use dynamic sql.
Note, that you can't use "SELECT to nowhere" in a compound statement in Db2. That is, the following code is erroneous.
BEGIN
SELECT * FROM MYTAB;
END#
This is why you need to store the result of SELECT somewhere. You may use Global Temporary Tables for that presuming, that USER TEMPORARY TABLESPASE is available to use for your user.
--#SET TERMINATOR #
BEGIN
DECLARE V_STMT VARCHAR (500);
SELECT
'DECLARE GLOBAL TEMPORARY TABLE SESSION.RESULT'
|| ' AS (SELECT * FROM '
|| MAIN
|| ') WITH DATA WITH REPLACE '
|| 'ON COMMIT PRESERVE ROWS NOT LOOGED'
INTO V_STMT
FROM XYZ
-- place your WHERE clause here if needed
FETCH FIRST 1 ROW ONLY
;
EXECUTE IMMEDIATE V_STMT;
END
#
SELECT * FROM SESSION.RESULT
#
dbfiddle link.
Here is a solution on stack that shows how to get the table names from your database
DB2 Query to retrieve all table names for a given schema
Then you could take your failure table and join into it based off of the table name, that should match your errors to the table that match on the table name. I'm not a 100% sure of your question but I think this is what you are asking.
The inner system query has schema and name. Type is T for table. See IBM link below for column reference. You could run the query wide open in the inner query to look for the tables you want. I would recommend using schema to isolate your search.
https://www.ibm.com/docs/en/db2-for-zos/11?topic=tables-systables
SELECT
ft.*
, st.*
FROM [FailureTable] as ft
INNER JOIN
(
select * from sysibm.systables
where CREATOR = 'SCHEMA'
and name like '%CUR%'
and type = 'T'
) st
ON st.[name] = ft.[tablename]
You can try
DECLARE #tableName VARCHAR(50);
SELECT #tableName = main
FROM xyx
EXEC('SELECT * FROM ' + 'dbo.' + #tableName)
Dont forget to add validation if #tableName doesnt get populated
I have 2 tables corporate and corporate_copy. Initially they were same in structure but people started added new columns into corporate and forgot do do so for corporate_copy.
Somewhere in the application there is less used functionality that copies data from corporate to corporate_copy and that kept failing without anyone noticing. Now I have to add 28 columns (ofcourse with same type and length and constraints etc....).
I know it can be done in one ALTER TABLE statement but I still feel it is lengthy task.
Do we have any luxury that will make copy table same as main table by keeping data and adding default values in newly added columns?
I am asking much but is there anything like that?
--Generate a dynamic query which contain all the missing column list and Execute it
--for eg I tried Something
BEGIN TRAN
DECLARE #SqlSelect NVARCHAR(MAX),#ColumnDeclaration VARCHAR(2000)
SELECT DISTINCT ' '+COLUMN_NAME+' '+ DATA_TYPE +' '+ISNULL(CONVERT(NVARCHAR(10), CHARACTER_MAXIMUM_LENGTH ),'')+' 'Missing_Column INTO #T FROM INFORMATION_SCHEMA.COLUMNS a
WHERE a.column_name not in (SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS b
WHERE b.table_name in ('Corporate_Copy'))
and a.table_name in ('Corporate')
SELECT #ColumnDeclaration=STUFF((
SELECT ', ' + Missing_Column
FROM #T
FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(max)'), 1, 1, '')
SET #SqlSelect=' ALTER TABLE Corporate_Copy Add'+ #ColumnDeclaration + ');'
PRINT #SqlSelect
ROLLBACK TRAN
You could use schema compare, found in SQL Server data tools (free) to generate a change script automatically.
But if this is just a copy, you could just run this:
DROP TABLE Corporate_Copy;
SELECT *
INTO Corporate_Copy
FROM Corporate;
It's not clear whether you really need to preserve the data in the copy. If so, it's not really a copy is it?
From SQL-Server 2015, you can use the following query to extract all different columns between 2 tables:
select distinct a.* from INFORMATION_SCHEMA.COLUMNS a
where a.column_name not in (select column_name from INFORMATION_SCHEMA.COLUMNS b
where b.table_name in ('tbl_A'))
and a.table_name in ('tbl_B')
order by a.column_name
The output gives you enough information to create a simple script to add the columns which are missing:
For exmaple:
Alter table tbl_A ADD res.Column_Name res.Data_Type ....
generate CREATE script in SSMS (right-click on table, then "script table as...")
Delete all things that already exists. Usually they are in the begining and it's a simple
change CREATE to ALTER ... ADD
That should be possible using SELECT INTO, for example the following SQL statement creates a backup copy of corporate:
SELECT * INTO corporate_copy
FROM corporate ;
I have imported a table to my database, and to get the number of columns and assign it to a variable I do
SELECT #HowManyColumns = COUNT(COLUMN_NAME)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE (TABLE_NAME = #table_name )
But it keeps telling that the count is 0!
If I do the same for other tables it works!
I have found that the column count of the table that is not working is more than 40 columns, Why is it not working...
The data is this
Since tables w/o columns don't exists, that can only mean that the WHERE clause is not satisfied. In other words, the table named as the value of #table_name does not exists. Since you say 'sometimes it work, and some does not' that would immediately point toward case sensitive deployments. Make sure you always use the correct name for the table, with the proper case, so your code work correctly on servers which are deployed with a case sensitive collation.
Try issuing
SELECT DISTINCT TABLE_NAME
FROM INFORMATION_SCHEMA
and check table name for case.
Try having the table name as a text string instead:
DECLARE
#table_name varchar(50),
#noOfColumns int
SET
#table_name = 'table_name'
SET
#noOfColumns =
(SELECT count(*)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = #table_name)
PRINT #noOfColumns
The answer you get is the number of columns in the #noOfColumns variable
I would like to get all of the column names from a MySQL table, loop through each column name and then run a stored procedure using those column names as a variable. Something to the effect of:
colnames = get column names from table
for each colname
if something changed then
do something
else
do something else
It looks like SHOW COLUMNS FROM myTable will give me the column names, but how would I get the column names into a loop?
I would really like to run all of this in a stored procedure using native SQL. Since I'm still learning the intricacies of MySQL, and this would really help out my project. Thanks for your help.
I think you want something like this:
DECLARE col_names CURSOR FOR
SELECT column_name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'tbl_name'
ORDER BY ordinal_position;
select FOUND_ROWS() into num_rows;
SET i = 1;
the_loop: LOOP
IF i > num_rows THEN
CLOSE col_names;
LEAVE the_loop;
END IF;
FETCH col_names
INTO col_name;
//do whatever else you need to do with the col name
SET i = i + 1;
END LOOP the_loop;
You can write a query against information_schema to get the column names:
SELECT column_name
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'tbl_name'
ORDER BY ordinal_position
The column names are then returned just as any data from a table would be.
How can I Select all columns from all tables from the DB, like:
Select * From *
in SQL Server 2008???
The table list it´s very very big, and have so many columns, is it possible to do it without writing the column names?
Or maybe make a select that returns the name of the tables.
This SQL will do this...
DECLARE #SQL AS VarChar(MAX)
SET #SQL = ''
SELECT #SQL = #SQL + 'SELECT * FROM ' + TABLE_SCHEMA + '.[' + TABLE_NAME + ']' + CHAR(13)
FROM INFORMATION_SCHEMA.TABLES
EXEC (#SQL)
Try this, works fine
SELECT * FROM INFORMATION_SCHEMA.COLUMNS
then you could add
WHERE TABLE_NAME LIKE '' AND COLUMN_NAME LIKE ''
SELECT t.name AS table_name,
SCHEMA_NAME(schema_id) AS schema_name,
c.name AS column_name
FROM sys.tables AS t
INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID where t.name = 'ProductItem' AND C.name like '%retail%'
ORDER BY schema_name, table_name
It is possible to retrieve the name of all columns from sys.columns
It is possible to retrieve the name of all table from sys.tables
But is impossible to retrieve all the data from all the tables. As soon as more than one table is involved in a query, a JOIN is necessary. Unless join conditions are provided, tables are joined as full Cartesian product, meaning each row from each table is matched with each row from ll other tables. Such a query as you request would produce for 10 tables with 10 records each no less than 10e10 records, ie. 100 billion records. I'm sure you don't want this.
Perhaps if you explain what you what to achieve, not how, we can help better.
To select * from each table, one after another, you can use the undocumented but well known sp_msforeachtable:
sp_msforeachtable 'select * from ?'
If you are going to send to Excel, I would suggest you use the export wizard and simply select all the tables there. In the object browser, put your cursor on the database name and right click. Chose Tasks - Export Data and follow the wizard. WHy anyone would want an entire database in Excel is beyond me, but that's the best way. If you need to do it more than once you can save the export in an SSIS package.
In SQL Server 2016 Management Studio ( Version: 13.0.15900.1), to get all column names in a specified table, below is the syntax:
**Select name from [YourDatabaseName].[sys].[all_columns]
where object_id=(Select object_id from [YourDatabaseName].[sys].[tables]
where name='YourTableName')**