Can i somehow declare variable as query result? - sql

Question

I have stored procedure which should use count of records in table, lets name it table1.
I know i can:
select count(*)
into variable_name
from table1
but i really want to keep procedure body as clean and simple as possible.
Can i put this query into declaration and set value of my variable as result of the query in the declaration section?

Answer 1

As Vivek and default Locale mentioned, a Select within a pl/sql-block (like funcitons or procedures) is totally ok.
But there is one place where i do it: We store create-scripts for automated integration-tests in plsql-scripts.
To make them readable they look like this:
DECLARE
sqlCreateTable VARCHAR2 (2000) :=
'CREATE TABLE TMyTableName
(
COL1 VARCHAR2(30 BYTE) NOT NULL,
COL2 VARCHAR2(30 BYTE) NOT NULL
)
TABLESPACE MYTABLESPACE
PCTUSED 0
PCTFREE 0
INITRANS 1
MAXTRANS 255
STORAGE (
INITIAL 1M
NEXT 1M
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0
BUFFER_POOL DEFAULT
)
LOGGING
NOCOMPRESS
NOCACHE
MONITORING';
sqlCreateIndex VARCHAR2 (2000) :=
'CREATE UNIQUE
[...]
)';
sqlCreateView VARCHAR2 (2000) :=
'CREATE OR REPLACE FORCE VIEW VMyTable
(
COL1,
COL2
)
BEQUEATH DEFINER
AS
SELECT COL1, COL2 FROM
FROM MyTableName';
BEGIN
-- |---------------------------------------------------------------------------|
-- | CREATE TABLE |
-- |---------------------------------------------------------------------------|
dbms_output.put_line('- - - - - - START - - - - - -');
dbms_output.put_line('CREATE TABLE:' || chr(10) || sqlCreateTable);
EXECUTE IMMEDIATE sqlCreateTable;
dbms_output.put_line('CREATE INDEX:' || chr(10) || sqlCreateIndex);
EXECUTE IMMEDIATE sqlCreateIndex;
dbms_output.put_line('CREATE VIEW:' || chr(10) || sqlCreateView);
EXECUTE IMMEDIATE sqlCreateView;
dbms_output.put_line('- - - - - - DONE - - - - - -');
END;
Short example to run a query and populate local variables:
DECLARE
myQuery VARCHAR2 (2000) := 'SELECT 1 from DUAL';
myVar NUMBER;
BEGIN
EXECUTE IMMEDIATE myQuery INTO myVar;
DBMS_OUTPUT.put_line ('MyVar: ' || myVar);
END;

Answer 2

The answer is there is no syntax to embed an implicit cursor within a declaration. The general syntax for declaring a variable or constant is:
identifier [constant] datatype := expression;
expression can be a function, for example:
k_somecount constant integer := some_lookup('whatever');
That might be a neat approach if the function is used in multiple places or has multiple steps etc.
I wondered if there was a way to use an XML expression, for example:
k_somecount constant integer := cast(xmlwhatever(mystic xquery incantation) as integer);
but it seems not (and if there was, I don't think you would like it).
There is no implicit cursor expression syntax such as the following:
-- Made-up syntax purely to illustrate what you might have been hoping existed:
k_somecount integer := (select count(*) from employees);

Answer 3

You can do it like this,
DECLARE
CURSOR c
IS SELECT last_name, first_name
FROM employee;
TYPE emp_tab IS TABLE OF c%ROWTYPE INDEX BY BINARY_INTEGER;
v_emp_tab emp_tab;
v_variable_count NUMBER;
BEGIN
OPEN c;
FETCH c BULK COLLECT INTO v_emp_tab;
v_variable_count := v_emp_tab.COUNT;
DBMS_OUTPUT.PUT_LINE(v_variable_count);
CLOSE c;
END;
/