You can not alter constraints ever but you can drop them and then recreate.

Have look on this

    ALTER TABLE your_table DROP CONSTRAINT ACTIVEPROG_FKEY1;

and then recreate it with `ON DELETE CASCADE` like this
   

    ALTER TABLE your_table
    add CONSTRAINT ACTIVEPROG_FKEY1 FOREIGN KEY(ActiveProgCode) REFERENCES PROGRAM(ActiveProgCode)
        ON DELETE CASCADE;

hope this help

No. We cannot alter the constraint, only thing we can do is drop and recreate it

    ALTER TABLE [TABLENAME] DROP CONSTRAINT [CONSTRAINTNAME]
    

&gt; Foreign Key Constraint

    Alter Table Table1 Add Constraint [CONSTRAINTNAME] Foreign Key (Column) References Table2 (Column) On Update Cascade On Delete Cascade
  

&gt;  Primary Key constraint

    Alter Table Table add constraint [Primary Key] Primary key(Column1,Column2,.....)
    

What is the difference between `std::system_clock` and `std::steady_clock`? (An example case that illustrate different results/behaviours would be great).

If my goal is to precisely measure execution time of functions (like a benchmark), what would be the best choice between `std::system_clock`, `std::steady_clock` and `std::high_resolution_clock`?

Difference between std::system_clock and std::steady_clock?

I&#39;m using Mocha to test a small module in my Express.js application. In this module, one of my functions returns an array. I want to test whether or not the array is correct for a given input. I am doing so like this:

    suite(&#39;getWords&#39;, function(){
        test(&quot;getWords should return list of numbers&quot;, function() {
            var result = [&#39;555&#39;, &#39;867&#39;, &#39;5309&#39;];
            assert.equal(result, getWords(&#39;555-867-5309&#39;));
        });
    });

When this runs, I get the following assertion error:
    
    AssertionError: [&quot;555&quot;,&quot;867&quot;,&quot;5309&quot;] == [&quot;555&quot;,&quot;867&quot;,&quot;5309&quot;]


However, when I change my test to an &lt;code&gt;assert.deepEqual&lt;/code&gt;, the test passes fine. I was wondering if it was a case of &lt;code&gt;==&lt;/code&gt; vs &lt;code&gt;===&lt;/code&gt;, but if I enter 

    [1,2,3] === [1,2,3]

into the node.js command line, I still get false. 

Why do arrays not compare the way other values do (e.g. &lt;code&gt;1 == 1&lt;/code&gt;)? and what is the difference between assert.equal and assert.deepEqual?



The difference between assert.equal and assert.deepEqual in Javascript testing with Mocha?

SQL How to Alter Constraint


Below is 1 of my constraint

    CONSTRAINT ACTIVEPROG_FKEY1 FOREIGN KEY(ActiveProgCode) REFERENCES PROGRAM(ActiveProgCode),

I want to add in 

    ON DELETE CASCADE

to the constraint above. 

How do i alter that existing constraint ACTIVEPROG_FKEY1 and add  

    ON DELETE CASCADE

to constraint ACTIVEPROG_FKEY1

Consider ACTIVEPROG_FKEY1 is at Table ACTIVEPROG

How to Alter Constraint

SQL How to Alter Constraint
Below is 1 of my constraint
<pre><code class="hljs language-scss">CONSTRAINT ACTIVEPROG_FKEY1 FOREIGN KEY(ActiveProgCode) REFERENCES PROGRAM(ActiveProgCode),
</code></pre>
I want to add in
<pre><code class="hljs language-objectivec">ON DELETE CASCADE
</code></pre>
to the constraint above.
How do i alter that existing constraint ACTIVEPROG_FKEY1 and add
<pre><code class="hljs language-objectivec">ON DELETE CASCADE
</code></pre>
to constraint ACTIVEPROG_FKEY1
Consider ACTIVEPROG_FKEY1 is at Table ACTIVEPROG

How to add a column to a SQL Server table with a default value that is equal to value of an existing column?

I tried this T-SQL statement:

    ALTER TABLE tablename 
    ADD newcolumn type NOT NULL DEFAULT (oldcolumn) 

but it&#39;s giving an error:

&gt; *The name &quot;oldcolumn&quot; is not permitted in this context. Valid
&gt; expressions are constants, constant expressions, and (in some
&gt; contexts) variables. Column names are not permitted.*

Add a column to a table with a default value equal to the value of an existing column

How can I send an email using T-SQL but email address is stored in a table? I want to loop through the table and be able to send email. I cannot find a good example of doing this so far.

How to send email from SQL Server?

I have a query like this (in a function):

    UPDATE some_table SET
      column_1 = param_1,
      column_2 = param_2,
      column_3 = param_3,
      column_4 = param_4,
      column_5 = param_5
    WHERE id = some_id;

Where `param_x` is a parameter of my function. Is there a way to NOT update those columns, for which the param is `NULL`? For example - if `param_4` and `param_5` are `NULL`, then update only the first three columns and leave old values for `column_4` and `column_5`.

The way I am doing it now is:

    SELECT * INTO temp_row FROM some_table WHERE id = some_id;

    UPDATE some_table SET
      column_1 = COALESCE(param_1, temp_row.column_1),
      column_2 = COALESCE(param_2, temp_row.column_2),
      column_3 = COALESCE(param_3, temp_row.column_3),
      column_4 = COALESCE(param_4, temp_row.column_4),
      column_5 = COALESCE(param_5, temp_row.column_5)
    WHERE id = some_id;

Is there a better way?

Don&#39;t update column if update value is null

Is there a way to define a named constant in a PostgreSQL query? For example:

    MY_ID = 5;
    SELECT * FROM users WHERE id = MY_ID;

Is there a way to define a named constant in a PostgreSQL query?

I have a table with `id`, `year` and `count`. 

I want to get the `MAX(count)` for each `id` and keep the `year` when it happens, so I make this query:

    SELECT id, year, MAX(count)
    FROM table
    GROUP BY id;

Unfortunately, it gives me an error: 

&gt; ERROR:  column &quot;table.year&quot; must appear in the GROUP BY clause or be
&gt; used in an aggregate function

So I try:

    SELECT id, year, MAX(count)
    FROM table
    GROUP BY id, year;

But then, it doesn&#39;t do `MAX(count)`, it just shows the table as it is. I suppose because when grouping by `year` and `id`, it gets the max for the `id` of that specific year.

So, how can I write that query? I want to get the `id`&#180;s `MAX(count)` and the year when that happens.

PostgreSQL MAX and GROUP BY

&gt; **Possible Duplicate:**  
&gt; [Why does Oracle 9i treat an empty string as NULL?](https://stackoverflow.com/questions/203493/why-does-oracle-9i-treat-an-empty-string-as-null)  

&lt;!-- End of automatically inserted text --&gt;

I have a table in Oracle 10g named `TEMP_TABLE` with only two columns - `id` and `description` just for the sake of demonstration.

The column `id` is a sequence generated primary key of type `NUMBER(35, 0) not null` and the column `DESCRIPTION` is a type of `VARCHAR2(4000) not null`.

The basic table structure in this case would look something like the following.

    +--------------+-----------+---------------+
    |Name          | Null?     | Type          |
    +--------------+-----------+---------------+
    |ID            | NOT NULL  | NUMBER(35)    |
    |DESCRIPTION   | NOT NULL  | VARCHAR2(4000)|
    +--------------+-----------+---------------+

After creating this table, I&#39;m trying to insert the following `INSERT` commands alternatively.

    INSERT INTO temp_table (id, description) VALUES (1, null); -&gt;unsuccessful
    INSERT INTO temp_table (id, description) VALUES (2, &#39;&#39;);   -&gt;unsuccessful

Both of them are unsuccessful as obvious because the `not null` constraint is enforced on the `DESCRIPTION` column.

In both of the cases, Oracle complains

    ORA-01400: cannot insert NULL into (&quot;WAGAFASHIONDB&quot;.&quot;TEMP_TABLE&quot;.&quot;DESCRIPTION&quot;)
 

**An empty string is treated as a `NULL` value in Oracle.**


----------

If I dropped the `not null` constraint on the `DESCRIPTION` column then the basic table structure would look like the following

    +--------------+-----------+---------------+
    |Name          | Null?     | Type          |
    +--------------+-----------+---------------+
    |ID            | NOT NULL  | NUMBER(35)    |
    |DESCRIPTION   |           | VARCHAR2(4000)|
    +--------------+-----------+---------------+

and both of the `INSERT` commands as specified would be successful. They would create two rows one with a `null` value and another with an empty string `&#39;&#39;` in the `DESCRIPTION` column of the `TEMP_TABLE`.

Now, if I issue the following `SELECT` command,

    SELECT * FROM temp_table WHERE description IS NULL;

then it fetches both the rows in which one has a `null` value and the other has an empty string `&#39;&#39;` in the `DESCRIPTION` column.

The following `SELECT` statement however retrieves no rows from the `TEMP_TABLE`

    SELECT * FROM temp_table WHERE description=&#39;&#39;;

It doesn&#39;t even retrieve the row which has an empty string in the `DESCRIPTION` column.


----------


Presumably, it appears that Oracle treats a `null` value and an empty string `&#39;&#39;` differently here which however doesn&#39;t appear to be the case with the `INSERT` statement in which both a `null` value and an empty string `&#39;&#39;` are prevented from being inserted into a column with a `not null` constraint. Why is it so?

null vs empty string in Oracle

I need to order transaction based on the currency.
However I need to implement a custom order by, which makes the USD to always comes on the top, and the rest should be ordered asc.

for example :

 - BHT 
 - USD 
 - MYR 
 - JYP

should be sorted like :

 - USD
 - BHT
 - JPY
 - MYR

Is there a simple way to handle this?


Custom Order in Oracle SQL

I am new on Oracle database, but I have one issue. 
On my Database server (server1) listener and database instance run correctly and I can use `sqlplus` to connect to this DB.
When I connect to database by using other server, I check the TNS configuration and it is correct but system says:                                    

&gt;     ERROR:
&gt;     ORA-12541: TNS:no listener

My database is Oracle 10gR2

So how can I solve this issue?

Oracle client ORA-12541: TNS:no listener

We are using UUID as primary key for out oracle DB, and trying to determine an appropriate max character length for the VARCHAR. Apparently this is 36 characters but we have noticed UUID&#39;S generated which are longer than this - up to 60 characters in length.
Does anyone know a suitable max char length for UUID??

UUID max character length

Is there a way to display all the views currently set on an oracle database via sql developer?

Thanks.

Content Type	Original Author	Original Content on Stackoverflow
Question	user1777711	View Question on Stackoverflow
Solution 1 - Sql	user1819920	View Answer on Stackoverflow
Solution 2 - Sql	andy	View Answer on Stackoverflow

How to Alter Constraint

Sql Problem Overview

Sql Solutions

Solution 1 - Sql

Solution 2 - Sql

The difference between assert.equal and assert.deepEqual in Javascript testing with Mocha?

Difference between std::system_clock and std::steady_clock?

Attributions