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1 .. -*- coding: utf-8 -*- |
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2 |
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3 RQL language (Relation Query Language) |
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4 ====================================== |
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5 |
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6 XXXFIXME MERGE WITH 16-rql.en.txt |
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7 |
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8 Introduction |
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9 ------------ |
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10 * RQL language focuses on browsing relations. |
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11 * Attributes are considered as particular relations. |
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12 * RQL is inspired from SQL but is a high level language. |
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13 * A good knowledge of Erudi's schemas defining the application is required. |
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14 |
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15 |
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16 Types of requests |
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17 ----------------- |
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18 |
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19 Search (`Any`) |
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20 query the repository to extract entities and/or attributes. |
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21 |
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22 Insertion (`INSERT`) |
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23 insert new entities in the database. |
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24 |
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25 Updates of entities, creation of relations (`SET`) |
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26 update existing entities in the database, or create relations between existing |
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27 entities |
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28 |
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29 Deletion of entities or relations (`DELETE`) |
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30 delete existing entities and relations from the database. |
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31 |
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32 |
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33 Variables and typing |
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34 -------------------- |
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35 |
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36 Entities and values to browse and/or select are set in the query through *variables* |
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37 which should be written in capital letters. |
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38 |
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39 The possible types for each variable can be deducted from the schema depending on |
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40 the conditions expressed in the query. |
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41 |
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42 You can force the possible types for a variable thanks to the special relation `is`. |
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43 |
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44 |
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45 |
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46 Built-in types |
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47 -------------- |
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48 * `String` (literal: between double or single quotes). |
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49 * `Int`, `Float` (separator is '.'). |
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50 * `Date`, `Datetime`, `Time` (literal: pattern YYYY/MM/DD[ hh:mm] or keywords |
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51 `TODAY` and `NOW`). |
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52 * `Boolean` (keywords `TRUE` et `FALSE`). |
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53 * keyword `NULL`. |
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54 |
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55 Operators |
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56 ---------- |
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57 * Logical operators: `AND`, `OR`, `,`. |
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58 * Mathematical operators: `+`, `-`, `*`, `/`. |
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59 * Comparison operators: `=`, `<`, `<=`, `>=`, `>`, `~=`, `LIKE`, `IN`. |
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60 |
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61 * The operator `=` is the default operator. |
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62 |
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63 * The operator `LIKE` / `~=` allows the use of the character `%` in a string |
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64 to indicate that the string should start/end with a prefix/suffix:: |
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65 |
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66 Any X WHERE X nom ~= 'Th%' |
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67 Any X WHERE X nom LIKE '%lt' |
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68 |
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69 * The operator `IN` allows to provide a list of possible values:: |
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70 |
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71 Any X WHERE X nom IN ('chauvat', 'fayolle', 'di mascio', 'thenault') |
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72 |
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73 Search query |
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74 ------------ |
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75 |
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76 [`DISTINCT`] <entity type> V1(, V2)\* |
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77 [`GROUPBY` V1(, V2)\*] [`ORDERBY` <orderterms>] |
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78 [`WHERE` <condition>] |
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79 [`LIMIT` <value>] [`OFFSET` <value>] |
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80 |
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81 :entity type: |
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82 Type of the selected variable |
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83 Special type `Any` is equivalent to not specify a type |
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84 :condition: |
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85 list of relations to browse following the pattern |
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86 `V1 relation V2|<static value>` |
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87 :orderterms: |
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88 Setting of the selection order : variable or column number followed by the |
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89 sorting method (`ASC`, `DESC`), ASC being the default value. |
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90 :note for grouped queries: |
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91 For grouped queries (e.g. using function `GROUPBY`), all the selected |
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92 variables must be grouped or aggregated. |
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93 |
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94 Examples - search |
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95 ~~~~~~~~~~~~~~~~~ |
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96 :: |
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97 |
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98 Any X WHERE X eid 53 |
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99 Personne X |
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100 Personne X WHERE X travaille_pour S, S nom "logilab" |
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101 Any E,COUNT(X) GROUPBY E ORDERBY EN WHERE X is E, E name EN |
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102 Any E,COUNT(X) GROUPBY E ORDERBY 2 WHERE X is E |
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103 |
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104 |
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105 Advanced features |
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106 ~~~~~~~~~~~~~~~~~ |
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107 * Aggregate functions: `COUNT`, `MIN`, `MAX`, `SUM`. |
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108 * String functions:`UPPER`, `LOWER`. |
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109 * Optional relations: |
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110 |
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111 * They allow to select entities related to others or not. |
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112 |
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113 * You should use `?` behind the variable to specify the relation to itself is |
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114 optional. |
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115 |
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116 - Project anomalies related to a version or not:: |
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117 |
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118 Any X,V WHERE X concerns P, P eid 42, X corrected_in V? |
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119 |
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120 - All the cards and the project they document otherwise :: |
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121 |
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122 Any C,P WHERE C is Card, P? documented_by C |
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123 |
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124 Negation |
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125 ~~~~~~~~ |
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126 * A query such as `Document X WHERE NOT X owned_by U` is equivalent to |
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127 "the documents which do not have relation `owned_by`". |
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128 * Whereas the query `Document X WHERE NOT X owned_by U, U login "syt"` |
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129 is equivalent to "the documents which do not have relation `owned_by` |
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130 with the user syt". They could have a relation with other users. |
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131 |
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132 |
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133 Identity |
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134 ~~~~~~~~ |
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135 |
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136 We could use the special relation `identity` in a query in order to add a |
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137 condition of identity between two variables. This is equivalent to ``is`` |
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138 in Python. |
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139 |
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140 Any A WHERE A comments B, A identity B |
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141 |
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142 returns the set of objects which comment themselves. The relation `identity` |
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143 is very usefull while defining security rules with `RQLExpressions`. |
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144 |
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145 Insertion queries |
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146 ----------------- |
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147 `INSERT` <entity type> V1(, <entity type> V2)\* `:` <assignments> |
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148 [`WHERE` <condition>] |
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149 |
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150 :assignments: |
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151 list of relations to assign such as `V1 relation V2|<static value>` |
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152 |
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153 The condition allow to define the variables we would use in assignments. |
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154 |
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155 Be careful, if a condition is specified, the insertion is done *for each result |
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156 returned by the condition*. |
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157 |
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158 Examples - insertion |
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159 ~~~~~~~~~~~~~~~~~~~~~ |
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160 * Insertion of a new person named 'bidule':: |
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161 |
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162 INSERT Person X: X name 'bidule' |
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163 |
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164 * Insertion of a new person named 'bidule', another named |
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165 'chouette' and a relation 'friend' between them:: |
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166 |
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167 INSERT Person X, Person Y: X name 'bidule', Y name 'chouette', X friend Y |
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168 |
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169 * Insertion of a new person named 'bidule' and a relation 'friend'with an |
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170 existing person 'chouette':: |
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171 |
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172 INSERT Person X: X name 'bidule', X friend Y WHERE Y name 'chouette' |
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173 |
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174 |
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175 Update queries |
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176 -------------- |
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177 `SET` <assignments> |
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178 [`WHERE` <condition>] |
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179 |
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180 Be careful, if a condition is specified, the update is done *for each result |
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181 returned by the condition*. |
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182 |
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183 Examples - update |
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184 ~~~~~~~~~~~~~~~~~ |
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185 * Renaming of the person named 'bidule' to 'toto', with change on the first name:: |
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186 |
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187 SET X name 'toto', X firstname 'original' WHERE X is 'Person', X name 'bidule' |
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188 |
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189 * Insertion of a relation of type 'know' between two objects linked with the relation |
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190 of type 'friend' :: |
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191 |
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192 SET X know Y WHERE X friend Y |
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193 |
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194 Deletion queries |
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195 ---------------- |
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196 `DELETE` (<entity type> V) | (V1 relation v2),... |
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197 [`WHERE` <condition>] |
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198 |
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199 |
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200 Be careful, if a condition is specified, the deletion is done *for each result |
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201 returned by the condition*. |
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202 |
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203 |
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204 Examples |
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205 ~~~~~~~~ |
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206 * Deletion of the person named 'toto':: |
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207 |
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208 DELETE Person X WHERE X name 'toto' |
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209 |
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210 * Deletion of all the relations of type 'friend' linked to the person named |
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211 'toto':: |
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212 |
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213 DELETE X friend Y WHERE X is 'Person', X name 'toto' |