1 .. -*- coding: utf-8 -*- |
1 .. -*- coding: utf-8 -*- |
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3 Le langage RQL (Relation Query Language) |
3 RQL language (Relation Query Language) |
4 ======================================== |
4 ====================================== |
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6 Voir la `documentation de RQL <file:///home/sandrine/src/fcubicweb/rql/doc/build/html/index.html>`_ . |
6 XXX see also RQL documentation in source rql/doc. |
7 |
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8 |
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9 [TODO] |
9 Introduction |
10 Specific link to RQL complete documentation to remove duplicated content. |
10 ------------ |
11 |
11 * RQL language focuses on browsing relations. |
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12 * Attributes are considered as particular relations. |
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13 * RQL is inspired from SQL but is a high level language. |
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14 * A good knowledge of Erudi's schemas defining the application is required. |
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15 |
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16 |
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17 Types of requests |
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18 ----------------- |
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19 |
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20 Search (`Any`) |
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21 query the repository to extract entities and/or attributes. |
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22 |
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23 Insertion (`INSERT`) |
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24 insert new entities in the database. |
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25 |
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26 Updates of entities, creation of relations (`SET`) |
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27 update existing entities in the database, or create relations between existing |
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28 entities |
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29 |
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30 Deletion of entities or relations (`DELETE`) |
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31 delete existing entities and relations from the database. |
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32 |
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33 |
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34 Variables and typing |
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35 -------------------- |
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36 |
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37 Entities and values to browse and/or select are set in the query through *variables* |
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38 which should be written in capital letters. |
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39 |
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40 The possible types for each variable can be deducted from the schema depending on |
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41 the conditions expressed in the query. |
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42 |
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43 You can force the possible types for a variable thanks to the special relation `is`. |
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44 |
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45 |
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46 |
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47 Built-in types |
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48 -------------- |
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49 * `String` (literal: between double or single quotes). |
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50 * `Int`, `Float` (separator is '.'). |
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51 * `Date`, `Datetime`, `Time` (literal: pattern YYYY/MM/DD[ hh:mm] or keywords |
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52 `TODAY` and `NOW`). |
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53 * `Boolean` (keywords `TRUE` et `FALSE`). |
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54 * keyword `NULL`. |
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55 |
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56 Operators |
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57 ---------- |
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58 * Logical operators: `AND`, `OR`, `,`. |
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59 * Mathematical operators: `+`, `-`, `*`, `/`. |
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60 * Comparison operators: `=`, `<`, `<=`, `>=`, `>`, `~=`, `LIKE`, `IN`. |
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61 |
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62 * The operator `=` is the default operator. |
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63 |
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64 * The operator `LIKE` / `~=` allows the use of the character `%` in a string |
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65 to indicate that the string should start/end with a prefix/suffix:: |
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66 |
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67 Any X WHERE X nom ~= 'Th%' |
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68 Any X WHERE X nom LIKE '%lt' |
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69 |
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70 * The operator `IN` allows to provide a list of possible values:: |
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71 |
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72 Any X WHERE X nom IN ('chauvat', 'fayolle', 'di mascio', 'thenault') |
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73 |
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74 Search query |
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75 ------------ |
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76 |
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77 [`DISTINCT`] <entity type> V1(, V2)\* |
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78 [`GROUPBY` V1(, V2)\*] [`ORDERBY` <orderterms>] |
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79 [`WHERE` <condition>] |
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80 [`LIMIT` <value>] [`OFFSET` <value>] |
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81 |
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82 :entity type: |
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83 Type of the selected variable |
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84 Special type `Any` is equivalent to not specify a type |
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85 :condition: |
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86 list of relations to browse following the pattern |
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87 `V1 relation V2|<static value>` |
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88 :orderterms: |
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89 Setting of the selection order : variable or column number followed by the |
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90 sorting method (`ASC`, `DESC`), ASC being the default value. |
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91 :note for grouped queries: |
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92 For grouped queries (e.g. using function `GROUPBY`), all the selected |
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93 variables must be grouped or aggregated. |
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94 |
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95 Examples - search |
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96 ~~~~~~~~~~~~~~~~~ |
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97 :: |
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98 |
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99 Any X WHERE X eid 53 |
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100 Personne X |
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101 Personne X WHERE X travaille_pour S, S nom "logilab" |
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102 Any E,COUNT(X) GROUPBY E ORDERBY EN WHERE X is E, E name EN |
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103 Any E,COUNT(X) GROUPBY E ORDERBY 2 WHERE X is E |
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104 |
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105 |
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106 Advanced features |
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107 ~~~~~~~~~~~~~~~~~ |
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108 * Aggregate functions: `COUNT`, `MIN`, `MAX`, `SUM`. |
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109 * String functions:`UPPER`, `LOWER`. |
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110 * Optional relations: |
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111 |
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112 * They allow to select entities related to others or not. |
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113 |
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114 * You should use `?` behind the variable to specify the relation to itself is |
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115 optional. |
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116 |
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117 - Project anomalies related to a version or not:: |
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118 |
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119 Any X,V WHERE X concerns P, P eid 42, X corrected_in V? |
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120 |
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121 - All the cards and the project they document otherwise :: |
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122 |
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123 Any C,P WHERE C is Card, P? documented_by C |
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124 |
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125 Negation |
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126 ~~~~~~~~ |
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127 * A query such as `Document X WHERE NOT X owned_by U` is equivalent to |
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128 "the documents which do not have relation `owned_by`". |
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129 * Whereas the query `Document X WHERE NOT X owned_by U, U login "syt"` |
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130 is equivalent to "the documents which do not have relation `owned_by` |
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131 with the user syt". They could have a relation with other users. |
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132 |
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133 |
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134 Identity |
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135 ~~~~~~~~ |
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136 |
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137 We could use the special relation `identity` in a query in order to add a |
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138 condition of identity between two variables. This is equivalent to ``is`` |
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139 in Python. |
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140 |
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141 Any A WHERE A comments B, A identity B |
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142 |
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143 returns the set of objects which comment themselves. The relation `identity` |
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144 is very usefull while defining security rules with `RQLExpressions`. |
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145 |
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146 Insertion queries |
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147 ----------------- |
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148 `INSERT` <entity type> V1(, <entity type> V2)\* `:` <assignments> |
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149 [`WHERE` <condition>] |
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150 |
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151 :assignments: |
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152 list of relations to assign such as `V1 relation V2|<static value>` |
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153 |
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154 The condition allow to define the variables we would use in assignments. |
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155 |
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156 Be careful, if a condition is specified, the insertion is done *for each result |
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157 returned by the condition*. |
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158 |
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159 Examples - insertion |
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160 ~~~~~~~~~~~~~~~~~~~~~ |
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161 * Insertion of a new person named 'bidule':: |
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162 |
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163 INSERT Person X: X name 'bidule' |
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164 |
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165 * Insertion of a new person named 'bidule', another named |
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166 'chouette' and a relation 'friend' between them:: |
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167 |
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168 INSERT Person X, Person Y: X name 'bidule', Y name 'chouette', X friend Y |
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169 |
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170 * Insertion of a new person named 'bidule' and a relation 'friend'with an |
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171 existing person 'chouette':: |
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172 |
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173 INSERT Person X: X name 'bidule', X friend Y WHERE Y name 'chouette' |
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174 |
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175 |
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176 Update queries |
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177 -------------- |
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178 `SET` <assignments> |
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179 [`WHERE` <condition>] |
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180 |
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181 Be careful, if a condition is specified, the update is done *for each result |
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182 returned by the condition*. |
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183 |
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184 Examples - update |
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185 ~~~~~~~~~~~~~~~~~ |
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186 * Renaming of the person named 'bidule' to 'toto', with change on the first name:: |
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187 |
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188 SET X name 'toto', X firstname 'original' WHERE X is 'Person', X name 'bidule' |
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189 |
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190 * Insertion of a relation of type 'know' between two objects linked with the relation |
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191 of type 'friend' :: |
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192 |
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193 SET X know Y WHERE X friend Y |
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194 |
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195 Deletion queries |
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196 ---------------- |
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197 `DELETE` (<entity type> V) | (V1 relation v2),... |
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198 [`WHERE` <condition>] |
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199 |
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200 |
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201 Be careful, if a condition is specified, the deletion is done *for each result |
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202 returned by the condition*. |
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203 |
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204 |
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205 Examples |
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206 ~~~~~~~~ |
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207 * Deletion of the person named 'toto':: |
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208 |
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209 DELETE Person X WHERE X name 'toto' |
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210 |
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211 * Deletion of all the relations of type 'friend' linked to the person named |
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212 'toto':: |
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213 |
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214 DELETE X friend Y WHERE X is 'Person', X name 'toto' |
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215 |
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216 |