How to use WHERE clause in Redshift?

Posted on by Author

How to use WHERE clause in Redshift?

The WHERE clause contains conditions that either join tables or apply predicates to columns in tables. Tables can be inner-joined by using appropriate syntax in either the WHERE clause or the FROM clause. Outer join criteria must be specified in the FROM clause.

How do I get data between two dates in redshift?

— show weeks between two dates select datediff(week, ‘2018-01-01’, ‘2018-12-31’) as numweeks; — show hours between since a specific date select datediff(hour, ‘2018-12-01’, sysdate) as numhours; DATEDIFF() accepts the same values as EXTRACT() and DATE_PART() for its first parameter (eg week , day , hour , etc).

What is rows unbounded preceding in redshift?

UNBOUNDED PRECEDING indicates that the window starts at the first row of the partition; offset PRECEDING indicates that the window starts a number of rows equivalent to the value of offset before the current row. UNBOUNDED PRECEDING is the default.

How do you use coalesce in redshift?

READ:   How is technology helpful for the progress of humanity?

Below is the syntax of coalesce function in redshift are as follows.

  1. COALESCE (Value1, Value2,…., ValueN);
  2. COALESCE (Argument1, Argument2,…., ArgumentN);
  3. Select column1, column2,…., COALESCE (column_name1, column_name2)

Can you do a case statement in a where clause?

CASE STATEMENT IN WHERE CLAUSE: We can use a case statement in Where, Order by and Group by clause. So, by using a CASE statement with the where condition displays the result.

Can we use CTE in redshift?

Common table expressions (CTEs) are a great way to break up complex queries. Using CTEs usually result in a more readable and maintainable query versus using subqueries.

Where is redshift timestamp?

select pg_timezone_abbrevs(); You can also find current information about time zones in the IANA Time Zone Database . The following table has examples of time zone formats. TIMESTAMPTZ columns store values with up to a maximum of six digits of precision for fractional seconds.

How do you tell the time in redshift?

GETDATE returns the current date and time in the current session time zone (UTC by default). It returns the start date or time of the current statement, even when it is within a transaction block.

READ:   What is ELSS fund in mutual fund?

What is rows between unbounded preceding and unbounded following?

As the first term after the ROWS keyword in a window Frame specification, UNBOUNDED PRECEDING means that the starting boundary is the first row in the partition, and UNBOUNDED FOLLOWING means that the ending boundary is the last row in the partition.

What is rows between unbounded preceding and current row?

The frame, ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW, means that the window consists of the first row of the partition and all the rows up to the current row. Each calculation is done over a different set of rows. For example, when performing the calculation for row 4, the rows 1 to 4 are used.

How does redshift avoid divide by zero error?

Method 1: SQL NULLIF Function

  1. Use NULLIF function in the denominator with second argument value zero.
  2. If the value of the first argument is also, zero, this function returns a null value.
  3. If the value of the first argument is not zero, it returns the first argument value and division takes place as standard values.
READ:   Is Russian widely spoken in Latvia?

Should I use null or empty string?

It depends on the domain you are working on. NULL means absence of value (i.e. there is no value), while empty string means there is a string value of zero length. For example, say you have a table to store a person’ data and it contains a Gender column.