In Delphi Firedac I have a very long query. I would like to reuse it just changing the name of a column via parameter like this
select f1, f2
from t1
where id = :par1
and :colimn_name = :value_name
Passing the :column_name parameter the reult query is like this:
select f1, f2
from t1
where id = 123
and 'department_name' = 'production'
with 2 '' wrapping the column name.
How can I avoid this, is there a specific way in FireDAC?
Thank you.
That's what FireDAC offers macros for: Substitution Variables
select f1, f2
from t1
where id = :par1
and &column_name = :value_name
Setting the actual columns goes this way:
myQuery.MacroByName('column_name').AsRaw := 'department_name';
Edit: As the column name happens to be a DB identifier, using AsIdentifier instead of AsRaw should work as well. That could even be necessary when the column name can be some reserved word in the DB and has to be quoted somehow.
Related
I am trying to build bigquery stored procedure where I need to pass the table name as a parameter. My code is:
CREATE OR REPLACE PROCEDURE `MKT_DS.PXV2DWY_CREATE_PROPERTY_FEATURES` (table_name STRING)
BEGIN
----step 1
CREATE OR REPLACE TABLE `MKT_DS.PXV2DWY_CREATE_PROPERTY_FEATURES_01` AS
SELECT DISTINCT XX.HH_ID, A.ECR_PRTY_ID, XX.ANCHOR_DT
FROM table_name XX
LEFT JOIN
(
SELECT DISTINCT HH_ID, ECR_PRTY_ID
FROM `analytics-mkt-cleanroom.Master.EDW_ECR_ECR_MAPPING`
WHERE HH_ID NOT LIKE 'U%'
AND ECR_PRTY_ID IS NOT NULL
)A
ON XX.HH_ID = A.HH_ID----one (HH) to many (ecr)
;
END;
CALL MKT_DS.PXV2DWY_CREATE_PROPERTY_FEATURES(`analytics-mkt-cleanroom.MKT_DS.Home_Services_Multi_Class_Aesthetic_Baseline_Final_Training_Sample`);
I followed a couple of similar questions here and here, tried writing an EXECUTE IMMEDIATE version of the above but not able to work out the right syntax.
I think issue is; the SELECT statement in my code is selecting multiple columns XX.HH_ID, A.ECR_PRTY_ID, XX.ANCHOR_DT and the EXECUTIVE IMMEDIATE setup is meant to work only for one column. But I'm not sure. Please advise. Thank you.
I am basically trying to write stored procedures for data pipeline building.
Hope below is helpful.
pass a parameter as a string.
CALL MKT_DS.PXV2DWY_CREATE_PROPERTY_FEATURES(`analytics-mkt-cleanroom.MKT_DS.Home_Services_Multi_Class_Aesthetic_Baseline_Final_Training_Sample`);
-->
CALL MKT_DS.PXV2DWY_CREATE_PROPERTY_FEATURES('analytics-mkt-cleanroom.MKT_DS.Home_Services_Multi_Class_Aesthetic_Baseline_Final_Training_Sample');
use EXECUTE IMMEDIATE since a table name can't be parameterized as a variable in a query.
----step 1
EXECUTE IMMEDIATE FORMAT("""
CREATE OR REPLACE TABLE `MKT_DS.PXV2DWY_CREATE_PROPERTY_FEATURES_01` AS
SELECT DISTINCT XX.HH_ID, A.ECR_PRTY_ID, XX.ANCHOR_DT
FROM `%s` XX
LEFT JOIN
(
SELECT DISTINCT HH_ID, ECR_PRTY_ID
FROM `analytics-mkt-cleanroom.Master.EDW_ECR_ECR_MAPPING`
WHERE HH_ID NOT LIKE 'U%%'
AND ECR_PRTY_ID IS NOT NULL
)A
ON XX.HH_ID = A.HH_ID----one (HH) to many (ecr)
;
""", table_name);
escape % in a format string with additional %
LIKE 'U%'
-->
LIKE 'U%%'
see PARSE_DATE not working in FORMAT() in BigQuery
I have a select that return a single column, using as where clause 4 columns, and I created a specific index for this query. When I do this select using Dbeaver, the result return in 30~50 milliseconds.
SELECT
column1
FROM
myTable
WHERE
column2 = a
AND column3 = b
AND (column4 = c AND column5 = d )
FOR READ ONLY WITH UR;
Now I created a procedure with this same simple select. The proc declare a P1, a 'cursor with return', do the select, open the cursor and close the P1. When I use the same dbeaver connection the result is returning between 1.2 ~ 1.6 seconds.
CREATE PROCEDURE myProc (
IN a DECIMAL(10),
IN b DECIMAL(10),
IN c DECIMAL(10),
IN d DECIMAL(10)
)
LANGUAGE SQL
DYNAMIC RESULT SETS 1
SPECIFIC myProc
P1: BEGIN
DECLARE cursor1 CURSOR WITH RETURN for
SELECT
column1
FROM
myTable
WHERE
column2 = a
AND column3 = b
AND (column4 = c AND column5 = d )
FOR READ ONLY WITH UR;
OPEN cursor1;
END P1
Is this huge return difference correct? If wrong, Is there something wrong in my procedure that justifies this return time difference? Or could be something wrong in the DB configuration or the server that justifies this difference, something like few resources in the DB server or something like the proc not using the index( I don't know if procs in the DB2 use the index by default like the queries )?
I am new in DB2 and new in procedures creation. Thank you in advance.
Best regards,
Luis
I don't know if is the best way, but I solved the problem using a solution that I read for SQL Server. The solution is create local variables that will receive the parameters values, and use the variable in the queries, to guarantee always the best execution plan. I didn't knew if this was valid to DB2, but my proc now has almost the same response time compared to query. Worked!
Link of SQL Server post: SQL Server: Query fast, but slow from procedure
In this link above a user called #Jake give this explanation:
"The reason this happens is because the procedures query plan is being cached, along with the parameters that were passed to it. On subsequent calls, this query plan generated will be reused with new parameters. This can cause problems because if the data is unevenly distributed, one parameter can generate a sub-optimal plan vs. another. Using local variables essentially does the same as OPTIMIZE FOR UNKNOWN because local variables cannot be sniffed."
I think that is the same for DB2, because worked. After I change these old procedures to use local variables my execution plan begun to use the indexes recently created
PRAGMA table_info(myTable)
This query selects all the info in a table, for example: if there are 2 columns in a table then this query will select all the column names, column types e.t.c
I just want add one clause i.e I want to get info of specific columns that I define in the query.
Like this:
PRAGMA table_info(myTable) where columnNames = 'a' and columnNames = 'b' // this is wrong query but I just mentioned it to make my question more clear.
How can I do this?
You can pragma_table_info() in a query with a WHERE clause:
SELECT *
FROM pragma_table_info('myTable') -- note the single quotes
WHERE name IN ('a', 'b') -- equivalent: name = 'a' OR name = 'b'
See the demo.
I use below code to get selected columns. But in the column item, why the table.getName() is alias name t1 or t2 and table.getAlias() is null?
Is any sample code to get the table name(Spark_Test_1, Spark_Test_2) and the alias table name(t1,t2) in the same time?
String sql = "SELECT t1.AsOfD,t1.ValidD,t1.urn,t1.Money FROM Spark_Test_1 as t1 join Spark_Test_2 as t2 on ( t1.AsOfD = t2.AsOfD)";
Statement statement = CCJSqlParserUtil.parse(sqlStr);
Select selectStatement = (Select) statement;
for (int i = 0; i < size; i++) {
Expression expression = ((SelectExpressionItem) selectitems.get(i))
.getExpression();
//System.out.println("Expression:" + expression);
if(expression instanceof Column){
Column col = (Column) expression;
Table table = col.getTable();
logger.info(table.getFullyQualifiedName());
logger.info(table.getAlias());
logger.info(table.getName());
}
}
This is not an issue but normal JSqlParser behaviour. JSqlParser gives you a structured way to look at your SQL but does no semantic processing. It is a parser.
Therefore for a column the tablename is in your example indeed the alias. JSqlParser does not resolve this alias to the real table name. You have to process the from items to get the tablenames its aliases and map it to your columns.
IMHO you should follow the path of TableNamesFinder to build a visitor that extracts your columns and additional gets your tables including name and alias. You have to be careful to use only the tables that are valid within your columns context, e.g.
select data.a from (select a from mydata) as data
Here data is an alias for a subsql and not for a table.
I have 14 fields which are similar and I search the string 'A' on each of them. I would like after that order by "position" field
-- some set in order to remove a lot of useless text
def col='col01'
select '&col' "Fieldname",
&col "value",
position
from oneTable
where &col like '%A%'
/
-- then for the second field, I only have to type two lines
def col='col02'
/
...
def col='col14'
/
Write all the fields which contains 'A'. The problem is that those field are not ordered by position.
If I use UNION between table, I cannot take advantage of the substitution variables (&col), and I have to write a bash in unix in order to make the replacement back into ksh. The problem is of course that database code have to be hard-coded in this script (connection is not easy stuff).
If I use a REFCURSOR with OPEN, I cannot group the results sets together. I have only one request and cannot make an UNION of then. (print refcursor1 union refcursor2; print refcursor1+refcursor2 raise an exception, select * from refcursor1 union select * from refcursor2, does not work also).
How can concatenate results into one big "REFCURSOR"? Or use a union between two distinct run ('/') of my request, something like holding the request while typing new definition of variables?
Thank you for any advice.
Does this answer your question ?
CREATE TABLE #containingAValueTable
(
FieldName VARCHAR(10),
FieldValue VARCHAR(1000),
position int
)
def col='col01'
INSERT INTO #containingAValueTable
(
FieldName , FieldValue, position
)
SELECT '&col' "Fieldname",
&col "value",
position
FROM yourTable
WHERE &col LIKE '%A%'
/
-- then for the second field, I only have to type two lines
def col='col02'
INSERT INTO...
/
def col='col14'
/
select * from #containingAValueTable order by postion
DROP #containingAValueTable
But I'm not totally sure about your use of the 'substitution variable' called "col" (and i only have SQL Server to test my request so I used explicit field names)
edit : Sorry for the '#' charcater, we use it so often in SQL Server for temporaries, I didn't even know it was SQL Server specific (moreover I think it's mandatory in sql server for creating temporary table). Whatever, I'm happy I could be useful to you.