Category: Database

Oracle Collection Instead of Dual

I’m still retrofitting a bunch of SQL queries to use bind_by_name and came across a strange scenario. I created a recursive query (STARTS WITH / CONNECT BY PRIOR) but I needed to grab the original value too. The quickest way to accomplish this was to union in something like “select 12345CDE as equipment_id from dual”. But the only way to get a bunch of these original values grafted onto the result set is to iterate through the array once to build my :placeholder1, :placeholder2, …, placeholderN placeholders and then iterate through the array again to bind each placeholder to its proper value.

I’ve been working with Oracle collections for LIKE and IN queries, and thought I could use a table that only exists within the query to glom the entire array into a single placeholder. It works! A query like

select column_value equipment_id from TABLE(sys.ODCIVARCHAR2LIST('12345CDE', '23456BCD', '34567ABC') );

Adds each of the values to my result set.

Which means I can use a query like “select column_value as equipment_id from TABLE(:myIDs)” and bind the collection to :myIDs.

Oracle – Collections and IN or LIKE Queries

I’ve been retrofitting a lot of PHP/SQL queries to use oci_bind_by_name recently. When using “IN” clauses, you can iterate through your array twice, but it’s an inefficient approach.

// Build the query string with a bunch of placeholders
$strQuery = "select Col1, Col2, Col3 from TableName where ColName IN (";
for($i=0; $i < count($array); $i++){
    if($i > 0){
        $strQuery = $strQuery . ", ";
    $strQuery = $strQuery . ":bindvar" . $i;
$strQuery = $strQuery . ")";
// Then bind each placeholder to something
for($i=0; $i < count($array); $i++){
    oci_bind_by_name($stmt, ":bindvar".$i, $array[$i]);

Building a table from the array data and using an Oracle collection object creates cleaner code and avoids a second iteration of the array:

$strQuery = "SELECT indexID, objName FROM table WHERE objName in (SELECT column_value FROM table(:myIds))";
$stmt = oci_parse($conn, $strQuery);

$coll = oci_new_collection($kpiprd_conn, 'ODCIVARCHAR2LIST','SYS');
foreach ($arrayValues as $strValue) {
oci_bind_by_name($stmt, ':myIds', $coll, -1, OCI_B_NTY);
oci_set_prefetch($stmt, 300);

A simple like clause is quite straight-forward

$strNameLikeString = "SomeName%";
$strQuery = "SELECT ds_dvrsty_set_nm from ds_dvrsty_set WHERE ds_dvrsty_set_nm LIKE :divsetnm ORDER BY ds_dvrsty_set_nm DESC fetch first 1 row only";

$stmt = oci_parse($connDB, $strQuery);
oci_bind_by_name($stmt, ":divsetnm", $strNameLikeString);
oci_set_prefetch($stmt, 300);

But what about an array of inputs essentially reproducing the LIKE ANY predicate in PostgreSQL? There’s not a direct equivalent in Oracle, and iterating through the array twice to build out a query WHERE (Field1 LIKE ‘Thing1%’ OR Field1 LIKE ‘Thing2%’ OR Field1 LIKE ‘Thing3%’) is undesirable. The with EXISTS allows me to create a LIKE ANY type query and only iterate through my array once to bind variables to placeholders using the same collection approach as was used with the IN clause.

$arrayLocs = array('ERIEPAXE%', 'HNCKOHXA%', 'LTRKARXK%');
$strQuery = "SELECT location_id, clli_code FROM network_location WHERE EXISTS (select 1 FROM TABLE(:likelocs) WHERE clli_code LIKE column_value)";
$stmt = oci_parse($connDB, $strQuery);

$coll = oci_new_collection($connDB, 'ODCIVARCHAR2LIST','SYS');
foreach ($arrayLocs as $strLocation) {
oci_bind_by_name($stmt, ':likelocs', $coll, -1, OCI_B_NTY);
print "<table>\n";
print "<tr><th>Loc ID</th><th>CLLI</th></tr>\n";
while ($row = oci_fetch_array($stmt, OCI_ASSOC+OCI_RETURN_NULLS)) {
    print "<tr><td>" . $row['LOCATION_ID'] . "</td><td>" . $row['CLLI_CODE'] . "</td></tr>\n";
print "</table>\n";

There are many different collection types in Oracle which can be used with oci_new_collection. A full list of the system collection types can be queried from the database.


PostgreSQL Sequences

I’m having a problem with a database refusing to change INSERTS to UPDATES on the ON CONFLICT condition — it insists that a ‘duplicate key value violates unique constraint’. A little time with a search engine tells me that sequences can get out of sync, and then you cannot insert items into the table. How do you know your sequence is out of sync?

SELECT NEXTVAL((SELECT PG_GET_SERIAL_SEQUENCE('"table_name"', 'name_of_column_with_sequence'))) as "NextValue", MAX("name_of_column_with_sequence") AS "Max Value" FROM "table_name";

So null seems like it would be a problem!

For future reference, when the next value is smaller than the max value in the table, the solution is to set the series value based on the max value

SELECT SETVAL((SELECT PG_GET_SERIAL_SEQUENCE('"table_name"', 'name_of_column_with_sequence')), (SELECT (MAX("name_of_column_with_sequence") + 1) FROM "table_name"), FALSE);

Oracle Function – Keeping Null Records With LISTAGG

I have been using LISTAGG to group a bunch of records together to be presented in a single HTML table cell. Problem is LISTAGG doesn’t do anything with null field values. As such, the data doesn’t line up across columns. The three ID values have two string values, which basically get centered in the cell. You cannot tell which ID value goes to which name value.

By adding a concatenation to the LISTAGG value, something will be included in the result set even when the record value is null.

Voila — records line up and I can tell the first ID doesn’t have an associated string value.

Oracle: Query Timestamp Today

I wanted a quick way to query a logging table for today’s records. I figured there had to be some way to put a variable “today” into the query rather than put in the numbers for the current date. Voila — a query that retrieves records where the timestamp is greater than or equal to today:

select *
from ossa_central_logging
where action_ts >= cast(trunc(current_timestamp) as timestamp)
order by action_ts desc;

Oracle – LISTAGG

I needed to collapse multiple rows into a single row — the circuits within a diversity set are stored within the ds_dvrsty_set_circuit table as individual rows & the ds_dvrsty_set_id links the multiple rows. What I wanted was a set ID, set name, and the list of circuits within the set.

To accomplish this, I found LISTAGG which is a little bit like STUFF in MSSQL. This query produces a single row for each diversity set that contains the set ID, the set name, and a comma delimited list of set members.

     (select ds_dvrsty_set.ds_dvrsty_set_nm from ds_dvrsty_set where ds_dvrsty_set_id = ds_dvrsty_set_circuit.ds_dvrsty_set_id) as set_name,
     LISTAGG(ds_dvrsty_set_circuit.circuit_design_id,  ',') WITHIN GROUP(ORDER BY ds_dvrsty_set_circuit.ds_dvrsty_set_id) AS member_circuits
     left outer join ds_dvrsty_set on ds_dvrsty_set.ds_dvrsty_set_id = ds_dvrsty_set_circuit.DS_DVRSTY_SET_ID
     ds_dvrsty_set_circuit.ds_dvrsty_set_id in (select distinct ds_dvrsty_set_id from ds_dvrsty_set_circuit where circuit_design_id in (14445678, 5078901) )
     ds_dvrsty_set.ds_dvrsty_set_nm like '43%'

Voila — exactly what I needed. If the searched circuit design IDs appear in more than one set, there is a new row for each set ID.

Oracle – Select Top

I discovered the “rownum” trick early in my usage of Oracle databases — especially useful for sampling data to see what’s in there, something like “select * from dataTable where rownum < 6” gets you the first five records. But that’s not suitable if you want to sort the records. In this particular case, I have a series of names. I want to find the highest number value in the series so I can name my object with the next sequential name.

Enter “fetch first”  … this appears to be available since 12c (so older database installations may still require a more convoluted solution):

SELECT set_name from set_data
WHERE set_name LIKE 'Something-With-A-Series-%'
ORDER BY set_name DESC
fetch first 1 row only;

Which returns the last name in the series.