{"id":832,"date":"2008-03-07T01:00:00","date_gmt":"2008-03-06T16:00:00","guid":{"rendered":"https:\/\/ecoop.net\/memo\/2008-03-07-1.html"},"modified":"2026-08-10T14:44:41","modified_gmt":"2026-08-10T05:44:41","slug":"2008-03-07-1","status":"publish","type":"post","link":"https:\/\/www.ecoop.net\/memo\/archives\/2008-03-07-1.html","title":{"rendered":"NULL \u306f\u300c\u5024\u304c\u306a\u3044\u300d\u306e\u3067\u306f\u306a\u304f\u300c\u5024\u304c\u4e0d\u660e\u300d"},"content":{"rendered":"

\nSQL \u3067\u306f NULL \u3092\u542b\u3080\u6f14\u7b97\u306f IS NULL, IS NOT NULL \u3068\u4e00\u90e8\u306e\u8ad6\u7406\u6f14\u7b97\u3092\u9664\u304d\u5e38\u306b\u623b\u308a\u5024\u304c NULL \u306b\u306a\u308a\u307e\u3059\u3002
\n\u3053\u306e\u7d50\u679c\u3068\u3057\u3066\u3001NULL \u3092\u5024\u306b\u6301\u3064\u30ec\u30b3\u30fc\u30c9\u3092 IS NULL \u4ee5\u5916\u3067\u62bd\u51fa\u3067\u304d\u306a\u304f\u306a\u308a\u307e\u3059\u3002
\n\u305f\u3068\u3048\u3070\u6975\u7aef\u306a\u4f8b\u3067\u3059\u304c<\/p>\n

SELECT NULL != NULL\n<\/p><\/blockquote>\n

\u304c true \u306b\u306a\u3089\u305a NULL \u306b\u306a\u3063\u305f\u308a\u3057\u307e\u3059(\u3064\u307e\u308a (NULL != NULL) IS NULL \u304c\u771f\u306b\u306a\u308b)\u3002
\n 
\n\u3053\u306e\u4ed5\u69d8\u306f Java \u3084 PHP \u306a\u3069\u306e\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u8a00\u8a9e\u304b\u3089\u8003\u3048\u308b\u3068\u4e0d\u53ef\u89e3\u306a\u3082\u306e\u306b\u3046\u3064\u308a\u307e\u3059\u304c\u3001 NULL \u306f\u5024\u304c\u5b58\u5728\u3057\u306a\u3044\u306e\u3067\u306f\u306a\u304f\u307e\u3060\u308f\u304b\u3063\u3066\u3044\u306a\u3044(unknown)\u3060\u3051\u306a\u306e\u3060\u3001\u3068\u8003\u3048\u308b\u3068\u30b9\u30c3\u30ad\u30ea\u3057\u307e\u3059\u3002
\n 
\n\u5024\u6bb5\u306e\u30ab\u30e9\u30e0\u306b null \u3092\u6301\u3064\u5546\u54c1\u306b\u3064\u3044\u3066\u8003\u3048\u308b\u3068\u304d\u3001\u305d\u306e\u5546\u54c1\u306f\u300c\u7121\u6599\u300d\u3067\u306f\u306a\u304f\u5024\u6bb5\u304c\u307e\u3060\u300c\u6c7a\u307e\u3063\u3066\u3044\u306a\u3044\u300d\u3060\u3051\u3002\u643a\u5e2f\u306e\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u304c null \u306e\u30e6\u30fc\u30b6\u304c\u3044\u305f\u306a\u3089\u3001\u305d\u306e\u4eba\u306f\u643a\u5e2f\u96fb\u8a71\u3092\u300c\u6301\u3063\u3066\u3044\u306a\u3044\u300d\u3068\u3044\u3046\u610f\u5473\u3067\u306f\u306a\u304f\u3001\u305d\u306e\u4eba\u304c\u643a\u5e2f\u96fb\u8a71\u3092\u6301\u3063\u3066\u3044\u308b\u304b\u300c\u308f\u304b\u3089\u306a\u3044\u300d\u3060\u3051\u3067\u3059\u3002
\n 
\n\u6307\u5b9a\u3057\u305f\u90e8\u7f72(department_id)\u4ee5\u5916\u306b\u3044\u308b\u793e\u54e1(employee)\u306e\u540d\u524d\u3092\u63a2\u3059\u4e0b\u8a18\u306e\u3088\u3046\u306a\u30af\u30a8\u30ea\u3092\u5b9f\u884c\u3057\u3066\u3082\u3001\u90e8\u7f72\u304c null \u306e\u793e\u54e1\u306e\u540d\u524d\u306f\u542b\u307e\u308c\u307e\u305b\u3093\u3002\u305d\u306e\u793e\u54e1\u304c 1 \u306e\u90e8\u7f72\u306b\u914d\u5c5e\u3055\u308c\u308b\u304b\u3082\u3057\u308c\u306a\u3044\u304b\u3089\u3067\u3059\u3002\n<\/p>\n

SELECT name FROM employee WHERE department_id != 1\n<\/p><\/blockquote>\n

null \u5024\u3082\u7d50\u679c\u306b\u542b\u3081\u305f\u3044\u5834\u5408\u306f\u4e0b\u8a18\u306e\u3088\u3046\u306b\u3057\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002\n<\/p>\n

SELECT name FROM employee WHERE department_id != 1 AND department_id IS NULL\n<\/p><\/blockquote>\n

 
\n0 \u3084 \u306b\u5305\u62ec\u7684\u306a\u304b\u3089\u3063\u307d(empty)\u3068\u3044\u3046\u610f\u5473\u3092\u6301\u305f\u305b\u305f\u308b\u306e\u3082\u4f1d\u7d71\u7684\u3067\u3044\u3044\u3067\u3059\u304c\u3001SQL \u3067\u306f 0, <\/em> \u3068 NULL \u3092\u533a\u5225\u3057\u3066\u6709\u52b9\u306b\u4f7f\u3046\u307b\u3046\u304c\u3088\u3055\u305d\u3046\u3067\u3059\u3002
\n 
\n\u53c2\u8003:
\n3\u5024\u8ad6\u7406\u3068NULL(CodeZine)<\/p>\n","protected":false},"excerpt":{"rendered":"

SQL \u3067\u306f NULL \u3092\u542b\u3080\u6f14\u7b97\u306f IS NULL, IS NOT NULL \u3068\u4e00\u90e8\u306e\u8ad6\u7406\u6f14\u7b97\u3092\u9664\u304d\u5e38\u306b\u623b\u308a\u5024\u304c NULL \u306b\u306a\u308a\u307e\u3059\u3002 \u3053\u306e\u7d50\u679c\u3068\u3057\u3066\u3001NULL \u3092\u5024\u306b\u6301\u3064\u30ec\u30b3\u30fc\u30c9\u3092 IS NULL \u4ee5\u5916\u3067\u62bd\u51fa\u3067\u304d\u306a … \u7d9a\u304d\u3092\u8aad\u3080 NULL \u306f\u300c\u5024\u304c\u306a\u3044\u300d\u306e\u3067\u306f\u306a\u304f\u300c\u5024\u304c\u4e0d\u660e\u300d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[141],"tags":[26,45],"class_list":["post-832","post","type-post","status-publish","format-standard","hentry","category-lifehack","tag-mysql","tag-postgresql"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/posts\/832","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/comments?post=832"}],"version-history":[{"count":1,"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/posts\/832\/revisions"}],"predecessor-version":[{"id":1743,"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/posts\/832\/revisions\/1743"}],"wp:attachment":[{"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/media?parent=832"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/categories?post=832"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ecoop.net\/memo\/wp-json\/wp\/v2\/tags?post=832"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}