PostgreSQL 8.3.7ʸ��
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9.18. ��ؿ�

��ؿ���ʣ��ͤ��ñ��η�̤�׻��ޤ�� 表9-41��表9-42��Ȥ߹��߽��ؿ��򼨤��ޤ�� ؿ��ü�ʹ�ʸ�˴ؤ��ͻ��項4.2.7��Ƥ��ޤ�

表 9-41. ��ѽ��ؿ�

�ؿ�	��Υǡ��	��ͷ�	��
`avg(expression)`	`smallint`, `int`, `bigint`, `real`, `double precision`, `numeric`, or `interval`	��ΰ��Ǥ��`numeric`��ư��ΰ��Ǥ��`double precision`��ʳ��ϰ��Υǡ��Ʊ��	��Ƥ��ͤ�ʿ��͡ʻ��ʿ�ѡ�
`bit_and(expression)`	`smallint`, `int`, `bigint`, or `bit`	��Υǡ��Ʊ��	��Ƥ��NULL��ͤΥӥå��ѡ��NULL��ͤ��ʤ��NULL
`bit_or(expression)`	`smallint`��`int`��`bigint`��ޤ�� `bit`	��Υǡ��Ʊ��	��Ƥ��NULL��ͤΥӥå��¡��NULL��ͤ��ʤ��NULL
`bool_and(expression)`	`bool`	`bool`	��Ƥ��Ϥ��ʤ�п��Ǥʤ��е�
`bool_or(expression)`	`bool`	`bool`	��ʤ��Ȥ�1�Ĥ��ͤ��ʤ�п��Ǥʤ��е�
`count(*)`		`bigint`	��ϹԤο�
`count(expression)`	��	`bigint`	`expression`��NULL�ͤ��ϹԤθĿ�
`every(expression)`	`bool`	`bool`	`bool_and`��
`max(expression)`	��Ƥ��󡢿��͡�ʸ��󡢤ޤ��ջ��﷿	��η��Ʊ��	��Ƥ��ͤˤ錄��`expression`�κ��
`min(expression)`	��Ƥ��󡢿��͡�ʸ��󡢤ޤ��ջ��﷿	��η��Ʊ��	��Ƥ��ͤˤ錄��`expression`�κǾ��
`sum(expression)`	`smallint`��`int`��`bigint`��`real`��`double precision`��`numeric`��ޤ��`interval`	`smallint`�ޤ��`int`��ΰ��Ǥ��`bigint`��`bigint`��ΰ��Ǥ��`numeric`��ư��ΰ��Ǥ��`double precision`��ʳ��ϰ��Υǡ��Ʊ��	��Ƥ��ͤˤ錄��`expression`��

�嵭�δؿ��ϡ�count�ؿ��1�Ԥ��򤵤�ʤ��ä��NULL�ͤ��֤��Ȥ��դ��Ƥ��äˡ��Ԥ��򤬤ʤ�sum�ؿ��ϡ�ͽ�ۤ��Ǥ��ǤϤʤ�NULL��֤��ޤ��ɬ�פǤ��С�NULL�򥼥��ȸ򴹤��Ū��coalesce�ؿ��Ȥ��ȤǤ��ޤ��

注意: bool_and��bool_or��ؿ��ɸ��SQL�ν��ؿ�every��any�ޤ��some��б��ޤ��any��some�ˤĤ��ƤǤ��ɸ��ι�ʸ�ˤ�ۣ�椵��褦�Ǥ��
SELECT b1 = ANY((SELECT b2 FROM t2 ...)) FROM t1 ...;
��ǡ�ANY�ϡ��䤤��碌��Ƭ�Ȥ⡢��򼰤��Ԥ��֤��Ȥ��齸��ؿ��Ȥ⸫�ʤ��Ȥ��Ǥ��ޤ��äơ��äơ��ν��ؿ��ɸ��̾��Ĥ��ޤ��

注意: ¾��SQL�ǡ��١��ƥ�Ǥκ�Ȥ˿Ƥ��桼��ϡ�count��ؿ��ơ��֥��Τ�Ŭ�Ѥ��ǽ�˶ä��뤫��Τ�ޤ��
SELECT count(*) FROM sometable;
�Τ褦��䤤��碌�ϥơ��֥��Τ��༡��Ѥ��PostgreSQL�ˤ��¹Ԥ��ޤ��

��ײ��Ͻ��ˤ褯��Ѥ��뽸��ؿ��表9-42�˼��ޤ�� ʤ��ϡ��Ū�˻��Ѥ��뽸��ؿ��Ȥκ��ɤ��̽Ф��ޤ�� ʬ�ˤ��N�ϡ��٤Ƥ��ϼ��NULL��ϹԤθĿ��ɽ��ޤ�� ٤Ƥξ��ˤơ��㤨��N��0�λ��ʤɷ׻��̵��̣�Ǥ��ˤ�NULL��֤��ޤ��

表 9-42. ��׽��Ѥν��ؿ�

�ؿ�	��η�	��ͤη�	��
`corr(Y, X)`	`double precision`	`double precision`	��ط��
`covar_pop(Y, X)`	`double precision`	`double precision`	�춦ʬ��
`covar_samp(Y, X)`	`double precision`	`double precision`	ɸ�ܶ�ʬ��
`regr_avgx(Y, X)`	`double precision`	`double precision`	��Ω�ѿ��ʿ�� (`sum(X)/N`)
`regr_avgy(Y, X)`	`double precision`	`double precision`	��¸�ѿ��ʿ�� (`sum(Y)/N`)
`regr_count(Y, X)`	`double precision`	`bigint`	ξ��NULL�Ȥʤ��ϹԤθĿ�
`regr_intercept(Y, X)`	`double precision`	`double precision`	(`X`, `Y`)��Ȥ߹�碌�Ƿ�ޤ롢��Ф��Ǿ��ˡ��Y��
`regr_r2(Y, X)`	`double precision`	`double precision`	��ط��
`regr_slope(Y, X)`	`double precision`	`double precision`	`X`, `Y`)��Ȥ߹�碌�Ƿ�ޤ롢�Ǿ��ˡ�˹礦��η��
`regr_sxx(Y, X)`	`double precision`	`double precision`	`sum(X^2) - sum(X)^2/N` �ʰ�¸�ѿ��"��"��
`regr_sxy(Y, X)`	`double precision`	`double precision`	`sum(XY) - sum(X) sum(Y)/N` �ʰ�¸�ѿ��Ω�ѿ��"��"��
`regr_syy(Y, X)`	`double precision`	`double precision`	`sum(Y^2) - sum(Y)^2/N` ��Ω�ѿ��"��"��
`stddev(expression)`	`smallint`��`int`�� `bigint`��`real`��`double precision`��ޤ��`numeric`	`double precision` for floating-point arguments, otherwise `numeric`	`stddev_samp`��Ū��̾
`stddev_pop(expression)`	`smallint`��`int`�� `bigint`��`real`��`double precision`��ޤ��`numeric`	��ư��ΰ��Ǥ�`double precision`��ʳ��Ǥ�`numeric`	��ͤ��Ф��ɸ��к�
`stddev_samp(expression)`	`smallint`��`int`�� `bigint`��`real`��`double precision`��ޤ��`numeric`	��ư��ΰ��Ǥ�`double precision`��ʳ��Ǥ�`numeric`	��ͤ��Ф��ɸ��ɸ��к�
`variance`(`expression`)	`smallint`��`int`�� `bigint`��`real`��`double precision`��ޤ��`numeric`	��ư��ΰ��Ǥ�`double precision`��ʳ��Ǥ�`numeric`	`var_samp`��Ū��̾
`var_pop`(`expression`)	`smallint`��`int`�� `bigint`��`real`��`double precision`��ޤ��`numeric`	��ư��ΰ��Ǥ�`double precision`��ʳ��Ǥ�`numeric`	��ͤ��Ф��ʬ��ɸ��к��μ��
`var_samp`(`expression`)	`smallint`��`int`�� `bigint`��`real`��`double precision`��ޤ��`numeric`	��ư��ΰ��Ǥ�`double precision`��ʳ��Ǥ�`numeric`	��ͤ��Ф��ɸ��ʬ��ɸ��ɸ��к��

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