Question

尝试创建一个函数来将Access中保留字括起来以进行SQL查询：

library(dplyr)

tester <- data.frame(names=c("Add", "Date", "Test", "DOB"))

bracket_access <- function(x) {x %>% gsub(c("ADD|ALL|Alphanumeric|ALTER|AND|ANY|Application|AS|ASC|Assistant|
AUTOINCREMENT|Avg|BETWEEN|BINARY|BIT|BOOLEAN|BY|BYTE|CHAR|CHARACTER|
COLUMN|CompactDatabase|CONSTRAINT|Container|Count|COUNTER|CREATE|CreateDatabase|
CreateField|CreateGroup|CreateIndex|CreateObject|CreateProperty|CreateRelation|
CreateTableDef|CreateUser|CreateWorkspace|CURRENCY|CurrentUser|DATABASE|DATE|
DATETIME|DELETE|DESC|Description|DISALLOW|DISTINCT|DISTINCTROW|Document|
DOUBLE|DROP|Echo|Else|End|Eqv|Error|EXISTS|Exit|FALSE|Field |Fields|
FillCache|FLOAT |FLOAT4 |FLOAT8|FOREIGN|Form |Forms|FROM|Full|FUNCTION|
GENERAL|GetObject|GetOption|GotoPage|GROUP|GROUP BY|GUID|HAVING|Idle|
IEEEDOUBLE|IEEESINGLE|If|IGNORE|Imp|IN|INDEX|Index|Indexes|INNER|
INSERT|InsertText|INT|INTEGER|INTEGER1 |INTEGER2 |INTEGER4|INTO|IS|
JOIN|KEY|LastModified|LEFT|Level|Like|LOGICAL |LOGICAL1|LONG |LONGBINARY|
LONGTEXT|Macro|Match|Max |Min |Mod|MEMO|Module|MONEY|Move|NAME|
NewPassword|NO|Not|Note|NULL|NUMBER |NUMERIC|Object|OLEOBJECT|OFF|ON|
OpenRecordset|OPTION|OR|ORDER|Orientation|Outer|OWNERACCESS|Parameter|
PARAMETERS|Partial|PERCENT|PIVOT|PRIMARY|PROCEDURE|Property|Queries|Query|
Quit|REAL|Recalc|Recordset|REFERENCES|Refresh|RefreshLink|RegisterDatabase|
Relation|Repaint|RepairDatabase|Report|Reports|Requery|RIGHT|SCREEN|SECTION|
SELECT|SET|SetFocus|SetOption|SHORT|SINGLE|SMALLINT|SOME|SQL|StDev|
StDevP|STRING|Sum|TABLE|TableDef|TableDefs|TableID|TEXT|TIME |TIMESTAMP|
TOP|TRANSFORM|TRUE|Type|UNION|UNIQUE|UPDATE|USER|VALUE|VALUES|Var|
VarP|VARBINARY|VARCHAR|VERSION|WHERE|WITH|Workspace|Xor|Year|YES|YESNO"), paste0("[",.,"]"), ignore.case = T)
}

bracket_access(tester)

我得到一个数字输出，但我真的不明白为什么：

> bracket_access(tester)
[1] "[c(1, 2, 4, 3)]"

Answer 1

您可以通过匹配并捕获与您提供的备用字符串相同的字符串，然后在names中将[\\1]列替换为gsub来解决当前方法：

bracket_access <- function(x) {
   gsub("^(ADD|ALL|Alphanumeric|ALTER|AND|ANY|Application|AS|ASC|Assistant|AUTOINCREMENT|Avg|BETWEEN|BINARY|BIT|BOOLEAN|BY|BYTE|CHAR|CHARACTER|COLUMN|CompactDatabase|CONSTRAINT|Container|Count|COUNTER|CREATE|CreateDatabase|CreateField|CreateGroup|CreateIndex|CreateObject|CreateProperty|CreateRelation|CreateTableDef|CreateUser|CreateWorkspace|CURRENCY|CurrentUser|DATABASE|DATE|DATETIME|DELETE|DESC|Description|DISALLOW|DISTINCT|DISTINCTROW|Document|DOUBLE|DROP|Echo|Else|End|Eqv|Error|EXISTS|Exit|FALSE|Field |Fields|FillCache|FLOAT |FLOAT4 |FLOAT8|FOREIGN|Form |Forms|FROM|Full|FUNCTION|GENERAL|GetObject|GetOption|GotoPage|GROUP|GROUP BY|GUID|HAVING|Idle|IEEEDOUBLE|IEEESINGLE|If|IGNORE|Imp|IN|INDEX|Index|Indexes|INNER|INSERT|InsertText|INT|INTEGER|INTEGER1 |INTEGER2 |INTEGER4|INTO|IS|JOIN|KEY|LastModified|LEFT|Level|Like|LOGICAL |LOGICAL1|LONG |LONGBINARY|LONGTEXT|Macro|Match|Max |Min |Mod|MEMO|Module|MONEY|Move|NAME|NewPassword|NO|Not|Note|NULL|NUMBER |NUMERIC|Object|OLEOBJECT|OFF|ON|OpenRecordset|OPTION|OR|ORDER|Orientation|Outer|OWNERACCESS|Parameter|PARAMETERS|Partial|PERCENT|PIVOT|PRIMARY|PROCEDURE|Property|Queries|Query|Quit|REAL|Recalc|Recordset|REFERENCES|Refresh|RefreshLink|RegisterDatabase|Relation|Repaint|RepairDatabase|Report|Reports|Requery|RIGHT|SCREEN|SECTION|SELECT|SET|SetFocus|SetOption|SHORT|SINGLE|SMALLINT|SOME|SQL|StDev|StDevP|STRING|Sum|TABLE|TableDef|TableDefs|TableID|TEXT|TIME |TIMESTAMP|TOP|TRANSFORM|TRUE|Type|UNION|UNIQUE|UPDATE|USER|VALUE|VALUES|Var|VarP|VARBINARY|VARCHAR|VERSION|WHERE|WITH|Workspace|Xor|Year|YES|YESNO)$", 
        "[\\1]", 
        x, 
        ignore.case = T)
}
bracket_access(tester$names)
## => [1] "[Add]"  "[Date]" "Test"   "DOB"

在这里，gsub模式看起来像^(word1|word2|...|wordN)$，一旦匹配，整个字符串就被[...]包裹并放回原处（\\1是一个占位符对于模式中的＃1捕获组，其中有一个定义了一对未转义的括号。

如何用括号括起来的单词来匹配单词？

1 个答案: