Hi Team how can we use cursor memsql,i did not saw any code using the cursor process in memesql procedure.
is there any other process to use cursor usage?
SingleStore DB (formerly known as MemSQL), has a COLLECT function where you can achieve read-only cursor functionality by calling COLLECT and iterating over the values in the resulting array. The array may be processed forwards, backwards or in an arbitrary order.
We have several use cases with sample SQL queries in our official documentation. I have included the first below as a reference:
Example 1: Using COLLECT with Static Queries
In the following example, COLLECT uses a query type variable, whose definition SELECT * from t is static.
DROP DATABASE IF EXISTS memsql_docs_example;
CREATE DATABASE memsql_docs_example;
USE memsql_docs_example;
CREATE TABLE t(id INT, name TEXT);
CREATE TABLE output_log(msg TEXT);
INSERT INTO t VALUES (1, 'red'), (2, 'green'), (3, 'blue');
DELIMITER //
CREATE OR REPLACE PROCEDURE p() AS
DECLARE
qry QUERY(id INT, name TEXT) = SELECT id, name FROM t;
arr ARRAY(RECORD(id INT, name TEXT));
_id INT;
_name TEXT;
BEGIN
arr = COLLECT(qry);
FOR x in arr LOOP
_id = x.id;
_name = x.name;
INSERT INTO output_log VALUES(CONCAT('[', _id, ', ', _name, ']'));
END LOOP;
END //
DELIMITER ;
CALL p();
SELECT * FROM output_log ORDER BY msg;
Cheers!
David, Education Delivery Specialist #
SingleStore DB (formerly MemSQL)
Some of my tables are of type REPLICATE. I would these tables to be actually replicated (not pending) before I start querying my data. This will help me avoid data movement.
I have a script, which I found online, which runs in a loop and do a SELECT TOP 1 on all the tables which are set for replication, but sometimes the script runs for hours. It may seem as the server sometimes won't trigger replication even if you do a SELECT TOP 1 from foo.
How can you force SQL Datawarehouse to complete replication?
The script looks something like this:
begin
CREATE TABLE #tbl
WITH
( DISTRIBUTION = ROUND_ROBIN
)
AS
SELECT
ROW_NUMBER() OVER(
ORDER BY
(
SELECT
NULL
)) AS Sequence
, CONCAT('SELECT TOP(1) * FROM ', s.name, '.', t.[name]) AS sql_code
FROM sys.pdw_replicated_table_cache_state AS p
JOIN sys.tables AS t
ON t.object_id = p.object_id
JOIN sys.schemas AS s
ON t.schema_id = s.schema_id
WHERE p.[state] = 'NotReady';
DECLARE #nbr_statements INT=
(
SELECT
COUNT(*)
FROM #tbl
), #i INT= 1;
WHILE #i <= #nbr_statements
BEGIN
DECLARE #sql_code NVARCHAR(4000)= (SELECT
sql_code
FROM #tbl
WHERE Sequence = #i);
EXEC sp_executesql #sql_code;
SET #i+=1;
END;
DROP TABLE #tbl;
SET #i = 0;
WHILE
(
SELECT TOP (1)
p.[state]
FROM sys.pdw_replicated_table_cache_state AS p
JOIN sys.tables AS t
ON t.object_id = p.object_id
JOIN sys.schemas AS s
ON t.schema_id = s.schema_id
WHERE p.[state] = 'NotReady'
) = 'NotReady'
BEGIN
IF #i % 100 = 0
BEGIN
RAISERROR('Replication in progress' , 0, 0) WITH NOWAIT;
END;
SET #i = #i + 1;
END;
END
Henrik, if 'select top 1' doesn't trigger a replicated table build, then that would be a defect. Please file a support ticket.
Without looking at your system, it is impossible to know exactly what is going on. Here are a couple of things that could be in factoring into extended build time to look into:
The replicated tables are large (size, not necessarily rows) requiring long build times.
There are a lot of secondary indexes on the replicated table requiring long build times.
Replicated table builds require statirc20 (2 concurrency slots). If the concurrency slots are not available, the build will queue behind other running queries.
The replicated tables are constantly being modified with inserts, updates and deletes. Modifications require the table to be built again.
The best way is to run a command like this as part of the job which creates/updates the table:
select top 1 * from <table>
That will force its redistribution at the correct time, without the slow loop through the stored procedure.
I have a parent/child table setup - Items/ItemDetails. This part works:
var q = db.From<Item>(); //various where clauses based on request
items = db.Select<Item>(q);
q = q.Select(a => a.ITEM_NO);
itemDetails = db.Select<ItemDetail>(x => Sql.In(x.ITEM_NO, q));
Trying to add paging to improve the performance of this request for large data sets, I'm having trouble getting the .Limit(skip, rows) function to work in the SQL.In statement of the child table.
var q = db.From<Item>().Limit(skip, rows);
items = db.Select<Item>(q);
q = q.Select(a => a.ITEM_NO);
itemDetails = db.Select<ItemDetail>(x => Sql.In(x.ITEM_NO, q));
It works when limiting the results in the first select, but when used in the child data pull I get "Only one expression can be specified in the select list when the subquery is not introduced with EXISTS."
The SQL that comes out changes the where subquery to:
WHERE "ITEM_NO" IN (SELECT * FROM (SELECT "ITEM_NO", ROW_NUMBER() OVER
(ORDER BY "ITEM"."ITEM_NO") As RowNum
FROM "ITEM") AS RowConstrainedResult WHERE RowNum > 5 AND RowNum <= 15)
I understand the SQL error is because I am selecting more than one column in the IN clause. Is there a better way to write this to avoid the error?
Thanks
If you're using SQL Server 2012 or later you should use SqlServer2012Dialect.Provider, e.g:
container.Register<IDbConnectionFactory>(c =>
new OrmLiteConnectionFactory(connString, SqlServer2012Dialect.Provider));
Which lets OrmLite use the paging support added in SQL Server 2012 instead of resorting to use the windowing function hack required to implement paging for earlier versions of SQL Server.
How can I make a package that returns results in table format when passed in csv values.
select * from table(schema.mypackage.myfunction('one, two, three'))
should return
one
two
three
I tried something from ask tom but that only works with sql types.
I am using oracle 11g. Is there something built-in?
The following works
invoke it as
select * from table(splitter('a,b,c,d'))
create or replace function splitter(p_str in varchar2) return sys.odcivarchar2list
is
v_tab sys.odcivarchar2list:=new sys.odcivarchar2list();
begin
with cte as (select level ind from dual
connect by
level <=regexp_count(p_str,',') +1
)
select regexp_substr(p_str,'[^,]+',1,ind)
bulk collect into v_tab
from cte;
return v_tab;
end;
/
Alas, in 11g we still have to handroll our own PL/SQL tokenizers, using SQL types. In 11gR2 Oracle gave us a aggregating function to concatenate results into a CSV string, so perhaps in 12i they will provide the reverse capability.
If you don't want to create a SQL type especially you can use the built-in SYS.DBMS_DEBUG_VC2COLL, like this:
create or replace function string_tokenizer
(p_string in varchar2
, p_separator in varchar2 := ',')
return sys.dbms_debug_vc2coll
is
return_value SYS.DBMS_DEBUG_VC2COLL;
pattern varchar2(250);
begin
pattern := '[^('''||p_separator||''')]+' ;
select trim(regexp_substr (p_string, pattern, 1, level)) token
bulk collect into return_value
from dual
where regexp_substr (p_string, pattern, 1, level) is not null
connect by regexp_instr (p_string, pattern, 1, level) > 0;
return return_value;
end string_tokenizer;
/
Here it is in action:
SQL> select * from table (string_tokenizer('one, two, three'))
2 /
COLUMN_VALUE
----------------------------------------------------------------
one
two
three
SQL>
Acknowledgement: this code is a variant of some code I found on Tanel Poder's blog.
Here is another solution using a regular expression matcher entirely in sql.
SELECT regexp_substr('one,two,three','[^,]+', 1, level) abc
FROM dual
CONNECT BY regexp_substr('one,two,three', '[^,]+', 1, level) IS NOT NULL
For optimal performance, it is best to avoid using hierarchical (CONNECT BY) queries in the splitter function.
The following splitter function performs a good deal better when applied to greater data volumes
CREATE OR REPLACE FUNCTION row2col(p_clob_text IN VARCHAR2)
RETURN sys.dbms_debug_vc2coll PIPELINED
IS
next_new_line_indx PLS_INTEGER;
remaining_text VARCHAR2(20000);
next_piece_for_piping VARCHAR2(20000);
BEGIN
remaining_text := p_clob_text;
LOOP
next_new_line_indx := instr(remaining_text, ',');
next_piece_for_piping :=
CASE
WHEN next_new_line_indx <> 0 THEN
TRIM(SUBSTR(remaining_text, 1, next_new_line_indx-1))
ELSE
TRIM(SUBSTR(remaining_text, 1))
END;
remaining_text := SUBSTR(remaining_text, next_new_line_indx+1 );
PIPE ROW(next_piece_for_piping);
EXIT WHEN next_new_line_indx = 0 OR remaining_text IS NULL;
END LOOP;
RETURN;
END row2col;
/
This performance difference can be observed below (I used the function splitter as was given earlier in this discussion).
SQL> SET TIMING ON
SQL>
SQL> WITH SRC AS (
2 SELECT rownum||',a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z'||rownum txt
3 FROM DUAL
4 CONNECT BY LEVEL <=10000
5 )
6 SELECT NULL
7 FROM SRC, TABLE(SYSTEM.row2col(txt)) t
8 HAVING MAX(t.column_value) > 'zzz'
9 ;
no rows selected
Elapsed: 00:00:00.93
SQL>
SQL> WITH SRC AS (
2 SELECT rownum||',a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z'||rownum txt
3 FROM DUAL
4 CONNECT BY LEVEL <=10000
5 )
6 SELECT NULL
7 FROM SRC, TABLE(splitter(txt)) t
8 HAVING MAX(t.column_value) > 'zzz'
9 ;
no rows selected
Elapsed: 00:00:14.90
SQL>
SQL> SET TIMING OFF
SQL>
I don't have 11g installed to play with, but there is a PIVOT and UNPIVOT operation for converting columns to rows / rows to columns, that may be a good starting point.
http://www.oracle.com/technology/pub/articles/oracle-database-11g-top-features/11g-pivot.html
(Having actually done some further investigation, this doesn't look suitable for this case - it works with actual rows / columns, but not sets of data in a column).
There is also DBMS_UTILITY.comma_to_table and table_to_comma for converting CSV lists into pl/sql tables. There are some limitations (handling linefeeds, etc) but may be a good starting point.
My inclination would be to use the TYPE approach, with a simple function that does comma_to_table, then PIPE ROW for each entry in the result of comma_to_table (unfortunately, DBMS_UTILITY.comma_to_table is a procedure so cannot call from SQL).
I want to perform a simple join on two tables (BusinessUnit and UserBusinessUnit), so I can get a list of all BusinessUnits allocated to a given user.
The first attempt works, but there's no override of Select which allows me to restrict the columns returned (I get all columns from both tables):
var db = new KensDB();
SqlQuery query = db.Select
.From<BusinessUnit>()
.InnerJoin<UserBusinessUnit>( BusinessUnitTable.IdColumn, UserBusinessUnitTable.BusinessUnitIdColumn )
.Where( BusinessUnitTable.RecordStatusColumn ).IsEqualTo( 1 )
.And( UserBusinessUnitTable.UserIdColumn ).IsEqualTo( userId );
The second attept allows the column name restriction, but the generated sql contains pluralised table names (?)
SqlQuery query = new Select( new string[] { BusinessUnitTable.IdColumn, BusinessUnitTable.NameColumn } )
.From<BusinessUnit>()
.InnerJoin<UserBusinessUnit>( BusinessUnitTable.IdColumn, UserBusinessUnitTable.BusinessUnitIdColumn )
.Where( BusinessUnitTable.RecordStatusColumn ).IsEqualTo( 1 )
.And( UserBusinessUnitTable.UserIdColumn ).IsEqualTo( userId );
Produces...
SELECT [BusinessUnits].[Id], [BusinessUnits].[Name]
FROM [BusinessUnits]
INNER JOIN [UserBusinessUnits]
ON [BusinessUnits].[Id] = [UserBusinessUnits].[BusinessUnitId]
WHERE [BusinessUnits].[RecordStatus] = #0
AND [UserBusinessUnits].[UserId] = #1
So, two questions:
- How do I restrict the columns returned in method 1?
- Why does method 2 pluralise the column names in the generated SQL (and can I get round this?)
I'm using 3.0.0.3...
So far my experience with 3.0.0.3 suggests that this is not possible yet with the query tool, although it is with version 2.
I think the preferred method (so far) with version 3 is to use a linq query with something like:
var busUnits = from b in BusinessUnit.All()
join u in UserBusinessUnit.All() on b.Id equals u.BusinessUnitId
select b;
I ran into the pluralized table names myself, but it was because I'd only re-run one template after making schema changes.
Once I re-ran all the templates, the plural table names went away.
Try re-running all 4 templates and see if that solves it for you.