\u4e00\u7bc7\u535a\u5ba2<\/a>
\nfound_return\uff0cfound_return\uff1a\u8fd9\u4e24\u4e2a\u662f\u8f93\u51fa\u53c2\u6570\uff0c\u8fd4\u56de\u6839\u636ewhere\u6761\u4ef6\u627e\u5230\u7684\u8bb0\u5f55\u6570\u548c\u5b9e\u9645\u53d1\u751f\u66f4\u65b0\u7684\u8bb0\u5f55\u6570
\n
\n\u4ecemysql_update\u88ab\u8c03\u7528\u7684\u5730\u65b9mysql_execute_command\uff0c\u89c2\u5bdf\u8fd9\u4e9b\u53c2\u6570\u662f\u4ece\u4ec0\u4e48\u5730\u65b9\u6765\u7684\uff1a<\/p>\n\r\nres= (up_result= mysql_update(thd, all_tables,\r\n select_lex->item_list,\r\n lex->value_list,\r\n select_lex->where,\r\n select_lex->order_list.elements,\r\n select_lex->order_list.first,\r\n unit->select_limit_cnt,\r\n lex->duplicates, lex->ignore,\r\n &found, &updated));\r\n<\/pre>\nfields <- thd->lex->select_lex.item_list
\nvalues <- thd->lex->values_list
\nconds <- thd->lex->select_lex.where<\/p>\n
\u5b9e\u9645\u4e0a\uff0c\u8fd9\u4e9b\u53c2\u6570\u90fd\u6765\u81ea\uff1athd->lex\uff0cMySQL\u652f\u6301\u7684\u6240\u6709\u652f\u6301\u7684SQL\/\u5b58\u50a8\u8fc7\u7a0b\/command\u5728\u901a\u8fc7lex\u548cyacc\u5206\u6790\u540e\u90fd\u4fdd\u5b58\u5728\u8fd9\u4e2a\u7ed3\u6784\u4e2d\uff0c\u8fd9\u7bc7\u535a\u5ba2\u53ea\u5173\u6ce8\u4e0eUPDATE\u8bed\u6cd5\u76f8\u5173\u7684<\/p>\n
update sql\u89e3\u6790\u8fc7\u7a0b<\/h3>\n
\u89e3\u6790\u5165\u53e3\uff1a<\/p>\n
\r\ndispatch_command\r\n|-->mysql_parse\r\n |-->parse_sql\r\n |-->MYSQLparse\r\n<\/pre>\n\u5728sql\/sql_yacc.cc\u4e2d<\/p>\n
\r\n#define yyparse MYSQLparse\r\n<\/pre>\n\u770b\u5230yyparse\u5e94\u8be5\u6709\u4e9b\u7709\u76ee\u4e86\uff0cmysql_parse\u89e3\u6790\u7684\u5bf9\u8c61\u662f\u5355\u6761SQL\uff0c \u82e5SQL\u4e3amulti-statement\uff0c\u4f1a\u4ee5\u5206\u53f7\u89e3\u6790\u6210\u591a\u6761SQL\u591a\u6b21\u8c03\u7528mysql_parse\uff0c\u8c03\u7528parse_sql\u4e4b\u524d\u90fd\u4f1a\u5148\u8c03\u7528lex_start\u6e05\u7406\u5185\u5b58\uff0c\u89e3\u6790\u89c4\u5219\u662f\u5728sql\/sql_yacc.yy\u4e2d\u5b9a\u4e49\uff0csql_yacc.yy\u6587\u4ef6\u88abgcc\u7f16\u8bd1\u540e\u4f1a\u81ea\u52a8\u751f\u6210\u5bf9\u5e94\u7684sql_yacc.cc\u6587\u4ef6\uff08\u8fd9\u4e2a\u5b9a\u4e49\u4e86\u4e00\u4e2a\u53ef\u6267\u884c\u7684\u81ea\u52a8\u72b6\u6001\u673a\uff0c\u4ee3\u7801\u57fa\u672c\u4e0d\u53ef\u8bfb\uff09<\/p>\n
sql\/sql_yacc.yy<\/h3>\n
\u5b9a\u4e49\u4e86\u4e00\u7cfb\u5217\u590d\u6742\u7684\u89c4\u5219\uff0c\u9700\u8981\u5173\u6ce8\u4e24\u4e2a\u89c4\u5219\uff1a
\nquery\uff1a\u6240\u6709\u7684statement\u90fd\u4f1a\u89c4\u7ea6\u5230\u8fd9\u4e2a\u89c4\u5219
\nstatement\uff1aMySQL\u652f\u6301\u7684\u5404\u79cdSQL\u5b9a\u4e49\uff0c\u5982\u679c\u8981\u6dfb\u52a0\u4e00\u79cdSQL\u8bed\u6cd5\uff0c\u9700\u8981\u5728statement\u89c4\u5219\u4e2d\u589e\u52a0\u4e00\u884c\uff0c\u5e76\u5728sql_yacc.yy\u6587\u4ef6\u4e2d\u5b9a\u4e49\u76f8\u5e94\u7684\u89c4\u5219\u63cf\u8ff0<\/strong><\/p>\n\u4e00\u79cd\u7b80\u5355\u65b9\u6cd5\u67e5\u627e\u4e00\u6761SQL\u5bf9\u5e94\u7684\u8bed\u6cd5\u89c4\u5219\u5b9a\u4e49\uff1a\u901a\u8fc7thd->lex_sql_command\u786e\u5b9aSQL\u7c7b\u578b\uff0c\u7136\u540e\u5728sql_yacc.yy\u4e2dgrep\u4e00\u4e0b\u5c31OK\u4e86<\/p>\n
\u5728sql_yacc.yy\u4e2d\u67e5\u770bstatement\u4e2dupdate\u89c4\u5219\u7684\u5b9a\u4e49<\/p>\n
\r\n\/* Update rows in a table *\/\r\nupdate:\r\n UPDATE_SYM\r\n { \r\n LEX *lex= Lex;\r\n mysql_init_select(lex);\r\n lex->sql_command= SQLCOM_UPDATE;\r\n lex->duplicates= DUP_ERROR; \r\n } \r\n opt_low_priority opt_ignore join_table_list\r\n SET update_list\r\n { \r\n LEX *lex= Lex;\r\n if (lex->select_lex.table_list.elements > 1)\r\n lex->sql_command= SQLCOM_UPDATE_MULTI;\r\n else if (lex->select_lex.get_table_list()->derived)\r\n { \r\n \/* it is single table update and it is update of derived table *\/\r\n my_error(ER_NON_UPDATABLE_TABLE, MYF(0),\r\n lex->select_lex.get_table_list()->alias, \"UPDATE\");\r\n MYSQL_YYABORT;\r\n } \r\n \/* \r\n In case of multi-update setting write lock for all tables may\r\n be too pessimistic. We will decrease lock level if possible in\r\n mysql_multi_update().\r\n *\/\r\n Select->set_lock_for_tables($3);\r\n } \r\n where_clause opt_order_clause delete_limit_clause {}\r\n ;\r\n\r\nupdate_list:\r\n update_list ',' update_elem\r\n | update_elem\r\n ;\r\n\r\nupdate_elem:\r\n simple_ident_nospvar equal expr_or_default\r\n {\r\n if (add_item_to_list(YYTHD, $1) || add_value_to_list(YYTHD, $3))\r\n MYSQL_YYABORT;\r\n }\r\n ;\r\n<\/pre>\n\u975e\u5e38\u6e05\u6670\u7684\u5b9a\u4e49\uff01field\u4fdd\u5b58\u5230\u4e86lex->select_lex.item_list\u4e2d\uff0c\u800cvalue\u4fdd\u5b58\u5728lex->value_list\u4e2d\uff0c\u5e76\u4e14\u5b83\u4eec\u662f\u4e00\u4e00\u5bf9\u5e94\u7684<\/strong><\/p>\n\u89c4\u5219\u662f\u5d4c\u5957\u5b9a\u4e49\u7684\uff0c\u5982\u679c\u60f3\u4e86\u89e3where\u6761\u4ef6\u600e\u4e48\u89e3\u6790\u7684\uff0c\u53ef\u4ee5\u67e5\u770b\u89c4\u5219where_clause\uff1a<\/p>\n
\r\nwhere_clause:\r\n \/* empty *\/ { Select->where= 0; }\r\n | WHERE\r\n {\r\n Select->parsing_place= IN_WHERE;\r\n }\r\n expr\r\n {\r\n SELECT_LEX *select= Select;\r\n select->where= $3;\r\n select->parsing_place= NO_MATTER;\r\n if ($3)\r\n $3->top_level_item();\r\n }\r\n ;\r\n<\/pre>\n\u6574\u4e2awhere\u6761\u4ef6\u4f1a\u88ab\u89c4\u7ea6\u6210\u4e00\u4e2aexpr\uff0c\u4fdd\u5b58\u5728lex->where\u4e2d<\/strong><\/p>\n\u4e0b\u9762\u4ee5\u4e00\u4e2a\u4f8b\u5b50\u8bf4\u660eupdate\u89e3\u6790\u540e\u7684\u7ed3\u679c\uff1a<\/p>\n
update t2 set b=b*2-1, c=c\/2+4 where id=5;<\/em><\/p>\nset\u5de6\u503c\u96c6\u5408\uff1afields<\/p>\n
\r\nthd->lex->select_lex.item_list\r\nList- \r\n|-->Item_field(b)\r\n|-->Item_field(c)\r\n<\/pre>\n
set\u53f3\u503c\u96c6\u5408\uff1avalues\uff1a<\/p>\n
\r\nthd->lex->value_list\r\nlist- \r\n|-->Item_func_minus\r\n |-->args[0]:Item_func_mul\r\n |-->args[0]:Item_field(b)\r\n |-->args[1]:Item_int(2)\r\n |-->args[1]:Item_int(1)\r\n|-->Item_func_plus\r\n |-->args[0]:Item_func_div\r\n |-->args[0]:Item_field(c)\r\n |-->args[1]:Item_int(2)\r\n |-->args[1]:Item_int(4)\r\n<\/pre>\n
where \u6761\u4ef6\uff1a<\/p>\n
\r\nthd->lex->select_lex.where\r\nItem_func_eq\r\n|-->args[0]:Item_field(id)\r\n|-->args[1]:Item_int(5)\r\n<\/pre>\nDebug Tips<\/h3>\n
1. \u5728sql_yacc.yy\u7684\u6587\u4ef6\u5934\u90e8\u52a0\u4e0a\u4e00\u884c
\n %verbose<\/em>
\nmake\u4e4b\u540e\u4f1a\u751f\u6210sql_yacc.output\u6587\u4ef6\uff0c\u5176\u4e2d\u6709\u5173\u72b6\u6001\u673a\u7684\u8be6\u7ec6\u4fe1\u606f\uff0c\u5305\u62ec\u5404\u4e2a\u72b6\u6001\u4e0e\u5b9a\u4e49\u89c4\u5219\u7684\u5bf9\u5e94\u5173\u7cfb\uff0cshift\/reduce\u884c\u4e3a\uff0c\u89c4\u5219\u51b2\u7a81\u4fe1\u606f<\/p>\n\r\nstate 568\r\n 1575 update: UPDATE_SYM $@142 . opt_low_priority opt_ignore join_table_list SET update_list $@143 where_clause opt_order_cla\r\nuse delete_limit_clause\r\n LOW_PRIORITY shift, and go to state 844\r\n $default reduce using rule 1582 (opt_low_priority)\r\n opt_low_priority go to state 936\r\n\r\nstate 936\r\n 1575 update: UPDATE_SYM $@142 opt_low_priority . opt_ignore join_table_list SET update_list $@143 where_clause opt_order_clause delete_limit_clause \r\n IGNORE_SYM shift, and go to state 120\r\n $default reduce using rule 910 (opt_ignore)\r\n opt_ignore go to state 1399\r\n<\/pre>\n\u6ce8<\/strong>\uff1a’.’\u8868\u793a\u5f53\u524d\u72b6\u6001\u5bf9\u5e94\u7684\u4f4d\u7f6e<\/p>\n2. \u542f\u52a8MySQL\u65f6\uff0c\u6253\u5f00parser_debug\u6807\u5fd7\u53ef\u4ee5\u770b\u5230sql\u89e3\u6790\u8fc7\u7a0b\u4e2d\u7684\u72b6\u6001\u8f6c\u79fb\u4fe1\u606f
\n \/u01\/mysql\/bin\/mysqld –defaults-file=\/u01\/mysql\/my.cnf –debug=”d,parser_debug” &<\/em>
\n\u89e3\u6790 \u201cupdate t2 set b=b*2-1, c=c\/2+4 where id=5\u201d \u65f6\u4ea7\u751f\u7684\u8c03\u8bd5\u4fe1\u606f\uff1a<\/p>\n\r\nStack now 0 53 568 936 1399 1844 2341 2753 3100 2230 2657\r\nEntering state 765\r\nReducing stack by rule 1575 (line 10698):\r\n $1 = token UPDATE_SYM ()\r\n $2 = nterm $@142 ()\r\n $3 = nterm opt_low_priority ()\r\n $4 = nterm opt_ignore ()\r\n $5 = nterm join_table_list ()\r\n $6 = token SET ()\r\n $7 = nterm update_list ()\r\n $8 = nterm $@143 ()\r\n $9 = nterm where_clause ()\r\n $10 = nterm opt_order_clause ()\r\n $11 = nterm delete_limit_clause ()\r\n-> $$ = nterm update ()\r\nStack now 0\r\nEntering state 90\r\nReducing stack by rule 58 (line 1771):\r\n $1 = nterm update ()\r\n-> $$ = nterm statement ()\r\nStack now 0\r\nEntering state 59\r\nReducing stack by rule 7 (line 1716):\r\n $1 = nterm statement ()\r\n-> $$ = nterm verb_clause ()\r\nStack now 0\r\nEntering state 58\r\nNext token is token END_OF_INPUT ()\r\nShifting token END_OF_INPUT ()\r\nEntering state 582\r\nReducing stack by rule 4 (line 1703):\r\n $1 = nterm verb_clause ()\r\n $2 = token END_OF_INPUT ()\r\n-> $$ = nterm query ()\r\nStack now 0\r\nEntering state 57\r\nReading a token: Now at end of input.\r\nShifting token $end ()\r\nEntering state 581\r\nStack now 0 57 581\r\nCleanup: popping token $end ()\r\nCleanup: popping nterm query ()\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"\u6700\u8fd1\u5728MySQL\u4e2d\u5b9e\u73b0\u4e86Oracle\/PostgreSQL\u4e2dUPDATE…RETURNING … \u7ee7\u7eed\u9605\u8bfbMySQL update\u8bed\u6cd5SQL\u89e3\u6790\u6e90\u7801\u5206\u6790<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false}}},"categories":[1],"tags":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p3tPZp-1T","jetpack_sharing_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/117"}],"collection":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=117"}],"version-history":[{"count":21,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/117\/revisions"}],"predecessor-version":[{"id":654,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=\/wp\/v2\/posts\/117\/revisions\/654"}],"wp:attachment":[{"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=117"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=117"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.gpfeng.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=117"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}