Setting All Values in Table = 0 Where Is Null
This page summarizes how NULL values are handled in CockroachDB SQL. Each issue is demonstrated via the reinforced-in SQL client.
Greenbac:
When using the reinforced-in client, Zip values are displayed using the word NULL. This distinguishes them from a character field that contains an empty string ("").
NULLs and simple comparisons
Any simple comparison betwixt a time value and NULL results in NULL. The remaining cases are described in the next section.
This behavior is consistent with PostgreSQL as well as all other starring RDBMS's.
> Cut-in INTO customers ( customer_id , cust_name , cust_email ) VALUES ( 1 , 'Smith' , Void );
> Make up TABLE t1 ( a INT , b INT , c INT );
> Put in INTO t1 VALUES ( 1 , 0 , 0 );
> INSERT INTO t1 VALUES ( 2 , 0 , 1 );
> INSERT INTO t1 VALUES ( 3 , 1 , 0 );
> Put in INTO t1 VALUES ( 4 , 1 , 1 );
> Enter INTO t1 VALUES ( 5 , NULL , 0 );
> INSERT INTO t1 VALUES ( 6 , NULL , 1 );
> INSERT INTO t1 VALUES ( 7 , NULL , NULL );
+---+------+------+ | a | b | c | +---+------+------+ | 1 | 0 | 0 | | 2 | 0 | 1 | | 3 | 1 | 0 | | 4 | 1 | 1 | | 5 | Nil | 0 | | 6 | NULL | 1 | | 7 | NULL | NULL | +---+------+------+
> SELECT * FROM t1 WHERE b < 10 ; +---+---+---+ | a | b | c | +---+---+---+ | 1 | 0 | 0 | | 2 | 0 | 1 | | 3 | 1 | 0 | | 4 | 1 | 1 | +---+---+---+
> SELECT * FROM t1 WHERE NOT b > 10 ; +---+---+---+ | a | b | c | +---+---+---+ | 1 | 0 | 0 | | 2 | 0 | 1 | | 3 | 1 | 0 | | 4 | 1 | 1 | +---+---+---+
> SELECT * FROM t1 WHERE b < 10 OR c = 1 ; +---+------+---+ | a | b | c | +---+------+---+ | 1 | 0 | 0 | | 2 | 0 | 1 | | 3 | 1 | 0 | | 4 | 1 | 1 | | 6 | Zilch | 1 | +---+------+---+
> Choice * FROM t1 WHERE b < 10 AND c = 1 ; +---+---+---+ | a | b | c | +---+---+---+ | 2 | 0 | 1 | | 4 | 1 | 1 | +---+---+---+
> SELECT * FROM t1 WHERE Non ( b < 10 AND c = 1 ); +---+------+---+ | a | b | c | +---+------+---+ | 1 | 0 | 0 | | 3 | 1 | 0 | | 5 | NULL | 0 | +---+------+---+
> Choose * FROM t1 WHERE NOT ( c = 1 AND b < 10 ); +---+------+---+ | a | b | c | +---+------+---+ | 1 | 0 | 0 | | 3 | 1 | 0 | | 5 | Cipher | 0 | +---+------+---+ Enjoyment the IS NULL or IS NOT Zipp clauses when checking for NULL values.
> SELECT * FROM t1 WHERE b IS NULL AND c IS NOT NULL ; +---+------+---+ | a | b | c | +---+------+---+ | 5 | NULL | 0 | | 6 | Cipher | 1 | +---+------+---+ NULLs and conditional operators
The conditional operators (including IF, Commingle, IFNULL) single evaluate about operands depending connected the prise of a condition operand, and then their result is not always NULL depending on the given operands.
E.g., COALESCE(1, NULL) testament e'er return 1 even though the second operand is NULL.
NULLs and ternary logic
AND, OR and IS follow out ternary logic, as follows.
| Expression | Result |
|---|---|
FALSE AND FALSE | FALSE |
FALSE AND TRUE | Mistaken |
FALSE AND Zip | FALSE |
TRUE AND FALSE | FALSE |
TRUE AND Lawful | TRUE |
TRUE AND NULL | NULL |
NULL AND Artificial | FALSE |
NULL AND TRUE | NULL |
Aught AND Zipp | NULL |
| Expression | Resultant role |
|---|---|
FALSE OR FALSE | FALSE |
FALSE Operating room TRUE | TRUE |
FALSE OR NULL | NULL |
TRUE OR FALSE | Avowedly |
TRUE OR TRUE | TRUE |
TRUE OR NULL | TRUE |
NULL Oregon FALSE | NULL |
NULL OR TRUE | Honorable |
Invalid OR NULL | Naught |
| Expression | Result |
|---|---|
FALSE IS Dishonorable | Honest |
Imitative IS TRUE | FALSE |
Fake IS Invalid | FALSE |
Dead on target IS Incorrect | FALSE |
True up IS TRUE | TRUE |
Apodeictic IS NULL | FALSE |
NULL IS FALSE | Mendacious |
NULL IS Real | FALSE |
NULL IS NULL | TRUE |
NULLs and pure mathematics
Arithmetic operations involving a NULL value will yield a Nil result.
> SELECT a , b , c , b * 0 , b * c , b + c FROM t1 ; +---+------+------+-------+-------+-------+ | a | b | c | b * 0 | b * c | b + c | +---+------+------+-------+-------+-------+ | 1 | 0 | 0 | 0 | 0 | 0 | | 2 | 0 | 1 | 0 | 0 | 1 | | 3 | 1 | 0 | 0 | 0 | 1 | | 4 | 1 | 1 | 0 | 1 | 2 | | 5 | NULL | 0 | Nada | NULL | NULL | | 6 | Nothing | 1 | NULL | NULL | Invalid | | 7 | NULL | NULL | NULL | NULL | Naught | +---+------+------+-------+-------+-------+ NULLs and aggregate functions
Aggregate functions are those that operate on a set of rows and return a single value. The example information has been repeated here to make information technology easier to understand the results.
+---+------+------+ | a | b | c | +---+------+------+ | 1 | 0 | 0 | | 2 | 0 | 1 | | 3 | 1 | 0 | | 4 | 1 | 1 | | 5 | NULL | 0 | | 6 | NULL | 1 | | 7 | NULL | NULL | +---+------+------+
> Blue-ribbon Bet ( * ), COUNT ( b ), SUM ( b ), AVG ( b ), MIN ( b ), MAX ( b ) FROM t1 ; +----------+----------+--------+--------------------+--------+--------+ | COUNT(*) | COUNT(b) | SUM(b) | AVG(b) | MIN(b) | Easy lay(b) | +----------+----------+--------+--------------------+--------+--------+ | 7 | 4 | 2 | 0.5000000000000000 | 0 | 1 | +----------+----------+--------+--------------------+--------+--------+ Note the following:
-
NULLvalues are non included in theCOUNT()of a column.Number(*)returns 7 whileCOUNT(b)returns 4. -
NULLvalues are non considered as malodourous or low values inMIN()orMAX(). -
AVG(b)returnsSUM(b)/COUNT(b), which is different thanAVG(*)asNULLvalues are not reasoned in theCOUNT(b)of rows. See NULLs A Other Values for Sir Thomas More details.
Zero as a distinct time value
NULL values are considered distinct from other values and are included in the list of separate values from a column.
> SELECT DISTINCT b FROM t1 ; +------+ | b | +------+ | 0 | | 1 | | NULL | +------+ However, counting the number of crystalline values excludes NULLs, which is consistent with the Calculate() social occasion.
> Choose COUNT ( Definite b ) FROM t1 ; +-------------------+ | count(DISTINCT b) | +-------------------+ | 2 | +-------------------+ NULLs as other values
In any cases, you may deprivation to include NULL values in pure mathematics or aggregate function calculations. To do so, use the IFNULL() function to substitute a assess for NULL during calculations.
For example, permit's say you want to bet the average value of column b as being the SUM() of all numbers in b divided by the total number of rows, disregardless of whether b's value is NULL. In this case, you would use AVG(IFNULL(b, 0)), where IFNULL(b, 0) substitutes a appreciate of naught (0) for Ciphers during the calculation.
> SELECT Reckon ( * ), COUNT ( b ), Center ( b ), AVG ( b ), AVG ( IFNULL ( b , 0 )), MIN ( b ), MAX ( b ) FROM t1 ; +----------+----------+--------+--------------------+--------------------+--------+--------+ | COUNT(*) | COUNT(b) | SUM(b) | AVG(b) | AVG(IFNULL(b, 0)) | Taiwanese(b) | Scoop(b) | +----------+----------+--------+--------------------+--------------------+--------+--------+ | 7 | 4 | 2 | 0.5000000000000000 | 0.2857142857142857 | 0 | 1 | +----------+----------+--------+--------------------+--------------------+--------+--------+ NULLs and set trading operations
NULL values are considered as part of a UNION set operation.
> SELECT b FROM t1 UNION Choice b FROM t1 ; +------+ | b | +------+ | 0 | | 1 | | Invalid | +------+ NULLs and sort
When sorting a chromatography column containing Naught values, CockroachDB sorts NULL values first with ASC and last with DESC. This differs from PostgreSQL, which sorts Goose egg values last with ASC and first with DESC.
Note that the NULLS Archetypical and NULLS Live on options of the ORDER BY clause are non implemented in CockroachDB, so you cannot change where NULL values appear in the sort order.
> Pick out * FROM t1 ORDER BY b ASC ; +---+------+------+ | a | b | c | +---+------+------+ | 6 | NULL | 1 | | 5 | NULL | 0 | | 7 | Zero | NULL | | 1 | 0 | 0 | | 2 | 0 | 1 | | 4 | 1 | 1 | | 3 | 1 | 0 | +---+------+------+
> Prime * FROM t1 Consecrate BY b DESC ; +---+------+------+ | a | b | c | +---+------+------+ | 4 | 1 | 1 | | 3 | 1 | 0 | | 2 | 0 | 1 | | 1 | 0 | 0 | | 7 | Invalid | NULL | | 6 | NULL | 1 | | 5 | NULL | 0 | +---+------+------+ NULLs and unique constraints
NULL values are not considered unique. Therefore, if a defer has a Unique constraint on one or more columns that are optional (nullable), it is possible to insert eight-fold rows with NULL values in those columns, every bit shown in the example below.
> CREATE TABLE t2 ( a INT , b INT UNIQUE );
> INSERT INTO t2 VALUES ( 1 , 1 );
> INSERT INTO t2 VALUES ( 2 , NULL );
> INSERT INTO t2 VALUES ( 3 , NULL );
+---+------+ | a | b | +---+------+ | 1 | 1 | | 2 | NULL | | 3 | NULL | +---+------+ NULLs and CHECK Constraints
A CHECK restraint expression that evaluates to NULL is considered to pass, allowing for apothegmatic expressions wish discount < price without worrying about adding OR discount IS NULL clauses. When non-null validation is desired, the usual NOT Zero constraint can be used along side a Check constraint.
> Make up TABLE products ( id STRING Direct KEY , Price INT NOT NULL CHECK ( price > 0 ), discount INT , Check over ( discount <= price ));
> Enclose INTO products ( id , price ) VALUES ( 'ncc-1701-d' , 100 );
> INSERT INTO products ( id , Price , disregard ) VALUES ( 'ncc-1701-a' , 100 , 50 );
> SELECT * FROM products ; +----------+-------+----------+ | id | cost | discount | +----------+-------+----------+ | ncc1701a | 100 | 50 | | ncc1701d | 100 | NULL | +----------+-------+----------+
> INSERT INTO products ( Idaho , price ) VALUES ( 'ncc-1701-b' , - 5 ); failed to satisfy Impediment restraint (Leontyne Price > 0)
> INSERT INTO products ( id , price , rebate ) VALUES ( 'ncc-1701-b' , 100 , 150 ); unsuccessful to live up to CHECK restraint (discount <= price) NULLs and chain with else types
Chain between a non-NULL value and a Zilch appreciate results in a Nil value.
Note:
In CockroachDB v20.2 and earlier, for all values other than STRING, concatenation between a not-NULL value and a NULL value results in an ARRAY of the non-NULL value's eccentric. To paying back an ARRAY of a specific type from a Nix concatenation in CockroachDB v21.1 and later, cast the Void value to an ARRAY.
For example:
?column? ------------ Nil (1 row)
?column? ------------ NULL (1 dustup) Was this page implemental?
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Atomic number 102
Setting All Values in Table = 0 Where Is Null
Source: https://www.cockroachlabs.com/docs/stable/null-handling.html
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