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COERCIBILITY

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Syntax

COERCIBILITY(str)

Description

Returns the collation coercibility value of the string argument. Coercibility defines what will be converted to what in case of collation conflict, with an expression with higher coercibility being converted to the collation of an expression with lower coercibility.

CoercibilityDescriptionExample
0ExplicitValue using a COLLATE clause
1No collationConcatenated strings using different collations
2ImplicitA string data type column value, CAST to a string data type
3System constantDATABASE(), USER() return value
4CoercibleLiteral string
5NumericNumeric and temporal values
6IgnorableNULL or derived from NULL

Examples

SELECT COERCIBILITY(_latin1 'abc' COLLATE latin1_swedish_ci);
+-----------------------------------------------+
| COERCIBILITY(_latin1 'abc' COLLATE latin1_swedish_ci) |
+-----------------------------------------------+
|                                             0 |
+-----------------------------------------------+

CREATE TABLE t (a VARCHAR(30) COLLATE uca1400_swedish_ai_ci, b VARCHAR(30) COLLATE uca1400_german2_ai_ci) CHARSET utf8mb4;
INSERT INTO t VALUES ('abc', 'def'); /* a 2 coercibility */
SELECT COERCIBILITY(CONCAT(a, b)) FROM t;
+----------------------------+
| COERCIBILITY(CONCAT(a, b)) |
+----------------------------+
|                          1 |
+----------------------------+

SELECT COERCIBILITY(CAST(1 AS CHAR));
+-------------------------------+
| COERCIBILITY(CAST(1 AS CHAR)) |
+-------------------------------+
|                             2 |
+-------------------------------+

SELECT COERCIBILITY(USER());
+----------------------+
| COERCIBILITY(USER()) |
+----------------------+
|                    3 |
+----------------------+

SELECT COERCIBILITY('abc');
+---------------------+
| COERCIBILITY('abc') |
+---------------------+
|                   4 |
+---------------------+

SELECT COERCIBILITY(1);
+-----------------+
| COERCIBILITY(1) |
+-----------------+
|               5 |
+-----------------+

SELECT COERCIBILITY(NULL);
+--------------------+
| COERCIBILITY(NULL) |
+--------------------+
|                  6 |
+--------------------+

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